November 2014 Hormones, Hairs & Hounds Programme

BVDSG Autumn Meeting – November 2014 Hormones, Hairs & Hounds

Programme

Saturday 15 th November

08.30 – 09.00 REGISTRATION

Morning Session – Chair: Filippo de Bellis

0 09.00 - 09.45 How do I approach the patient with alopecia? Manon Paradis

09.45 – 10.30 Hypothyroidism – cutaneous and non-cutaneous signs Michael Herrtage

10.30 – 11.00 COFFEE & COMMERCIAL EXHIBITION

11.00 – 11.45 Laboratory tests, drug influences and therapy of hypothyroidism Michael Herrtage

11.45 – 12.30 Hyperadrenocorticism – cutaneous and non-cutaneous signs Michael Herrtage

12.30 – 14.00 LUNCH & COMMERCIAL EXHIBITION

Afternoon Session – Chair: Inge Geens

14.00 – 14.45 Diagnosis and treatment of HAC Michael Herrtage

14.45 – 15.30 Atypical hyperadrenocorticism Michael Herrtage

15.30 – 16.15 COFFEE & COMMERCIAL EXHIBITION

16.15 – 17.00 The skin as a marker for internal disease Michael Herrtage

17.00 – 18.00 AGM

18.00 – 19.00 Drinks, gala dinner from 19.00

Programme continued

Sunday 15 th November

Morning Session – Chair: Sarah Warren

0 09.00 – 09.45 Introduction to histopathology of alopecia Trevor Whitbread

09.45 – 10.30 Follicular dysplasias Manon Paradis

10.30 – 11.00 COFFEE & COMMERCIAL EXHIBITION

11.00 – 11.45 Autoimmune alopecias Manon Paradis

11.45 – 12.30 Alopecia X Manon Paradis

12.30 – 14.00 LUNCH & COMMERCIAL EXHIBITION

Afternoon Session – Chair: Peri Lau-Gillard

14.00 – 14.45 Infectious causes of alopecia - fungi, bacteria and parasites Manon Paradis

14.45 – 15.30 Case discussions Manon Paradis

15.30 Abstracts

Contents

How do I approach the patient with alopecia? Page 7 M Paradis

Hypothyroidism – cutaneous and non-cutaneous signs Page 13 M Herrtage

Laboratory tests, drug influences and therapy of hypothyroidism Page 17 M Herrtage

Hyperadrenocorticism – cutaneous and non-cutaneous signs Page 23 M Herrtage

Diagnosis and treatment of HAC Page 33 M Herrtage

Atypical hyperadrenocorticism Page 53 M Herrtage

The skin as a marker for internal disease Page 57 M Herrtage

Introduction to histopathology of alopecia Page 61 T Whitbread

Follicular dysplasias Page 81 M Paradis

Autoimmune alopecias Page 95 M Paradis

Alopecia X Page 105 M Paradis

Infectious causes of alopecia - fungi, bacteria and parasites Page 113 M Paradis

Case discussions Page 121 M Paradis

Abstracts Page 125 R Morris

HOW DO I APPROACH THE PATIENT

WITH ALOPECIA ?

Manon Paradis, DMV, MScV, Dipl. ACVD, Department of clinical sciences, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.

Dr Manon Paradis is professor in veterinary dermatology at the Faculty of veterinary medicine of the University of Montreal. This is where she graduated in 1979 and pursued a small animal internship. Then, she completed a Residency in Small Animal Internal Medicine and a Master degree in Endocrinology at the University of Saskatchewan. This was followed by an Alternative Residency Program in Veterinary Dermatology with Dr Danny W Scott. She became a diplomate of the American College of Veterinary Dermatology in 1990. Dr Paradis' fields of interest include canine alopecia, hypothyroidism, genodermatoses and the use of avermectins and melatonin in small animal dermatology. She is author and co-author of over 100 scientific articles and 30 book chapters, and has given over 250 continuing education lectures at national and international meetings.

INTRODUCTION

Causes of alopecia are numerous in dogs and include infections (e.g. dermatophytes, demodicosis, bacterial folliculitis, leishmaniasis), self-inflicted hair loss (from hypersensitivities or parasitism), immune-mediated diseases (sebaceous adenitis, dermatomyositis, alopecia areata, etc.) endocrinopathies, follicular dysplasias, etc.

Hair growth is influenced, among other things, by gonadal, adrenal, thyroidal, pituitary and pineal hormones. Excesses, deficiencies and hormonal imbalances have been incriminated in a myriad of clinical syndromes in dogs. In some endocrinopathies (e.g., hypothyroidism, hyperadrenocorticism, hyperoestrogenism and pituitary dwarfism) the hormonal implication is well understood and these disorders are relatively well characterized clinically. However, other alopecic disorders may resemble endocrinopathies clinically (e.g., canine recurrent flank alopecia, alopecia-X, colour dilution alopecia and other follicular dysplasias) and, in many instances, the final diagnosis can be more difficult to establish. The aim of this presentation is to provide the clinician with a methodical clinical approach to canine alopecia, especially the non-pruritic, non-inflammatory, symmetrical hair losses.

CLINICAL APPROACH

A complete history should be taken and a general physical examination conducted to detect any abnormality present in other organs. A history of polyuria-polydipsia, the presence of a pendulous abdomen or abnormal genitalias (testicular asymmetry or cryptorchidism, vulvar enlargement) may greatly influence further tests to be carried out. The history and the dermatological examination should allow the clinician to rule in/out the presence of pruritus. If present, it should be investigated first. If pruritus is absent or minimal, one should determine whether the pattern of hair loss is focal or symmetric and diffuse. In addition, one should look for presence of inflammation and/or any primary lesions such as papules and pustules. Skin scrapings, skin cytology and/or dermatophyte cultures are often indicated if such skin lesions are present. If pruritus, inflammation or any other primary lesions are absent, the next most pertinent diagnostic procedure to perform will be influenced by age of onset, breed and sexual status.

1. SIGNALMENT AND HISTORY

Consideration of the dog’s age at the time of onset of alopecia, the rate of progression of the alopecia, its spontaneous resolution or its progression, and the presence of a cyclical pattern will help in compiling a list of differential diagnoses.

AGE AND TIME OF ONSET

The onset of alopecia should always be related to the dog’s age and any physiological and/or pathological event, management change or treatment. Alopecia sometimes occurs a few weeks after physiological events, such as pregnancy and lactation, or pathological events, such as severe systemic disease, shock or surgery (e.g., telogen defluxion). Failure of hair regrowth after clipping is suggestive of hypothyroidism, hyperadrenocorticism and alopecia-X. In Nordic breeds it is a common finding as in these breeds hair follicle cycle is longer than in other breeds.

Many disorders have an age at onset that is quite predictable. Congenital alopecia is present at birth; canine pattern alopecia often develops between 6 and 12 months of age, demodicosis usually occurs before 1 year of age. Clinical signs due to hypothyroidism typically develop between 3 to 6 years of age, and spontaneous hyperadrenocorticism occurs generally in middle-aged to old dogs.

BREED

Some breeds are predisposed to alopecic conditions such as alopecia-X (e.g., Pomeranian, Keeshound, Malamute, and miniature poodle), canine pattern alopecia (e.g., Dachshund, Chihuahua) and canine recurrent flank alopecia (e.g., boxer, airdale).

COAT COLOUR

Coat colour may provide useful diagnostic information in colour-linked alopecia such as black hair follicular dysplasia, colour dilution alopecia, and follicular lipidosis.

SEXUAL STATUS

Hyperoestrogenism due to Sertoli's-cell tumours and ovarian cysts or tumours may lead to alopecia. Prolonged oestrus can be seen in bitches with hyperestrogenism whereas anoestrus has been reported in bitches with hyperadrenocorticism and hypothyroidism.

SPONTANEOUS REMISSION

Spontaneous remission usually occurs in canine recurrent flank alopecia, anagen and telogen defluxions, and post-clipping alopecia not secondary to endocrinopathies. Alopecia areata may also resolve spontaneously and is often associated with regrowth of white hair (leucotrichia). Spontaneous remission is also seen in localized demodicosis and dermatophytosis; however, clinical inflammation and scaling is usually observed.

PROGRESSION

Slow progression of alopecia is more indicative of a systemic problem (e.g., endocrinopathies). Seasonality is more indicative of canine recurrent flank alopecia or flea allergy dermatitis.

SIGNS OF INTERNAL DISEASE

Owners of dogs with hyperadrenocorticism often report polyuria, polydipsia and polyphagia. In canine hypothyroidism, the owner may describe signs that reflect the slowing of metabolism, such as lethargy and weight gain.

PREVIOUS TREATMENTS

Endogenous and exogenous corticosteroids are notorious in causing Cushing's syndrome. One should not underestimate the effect of corticosteroids on hair growth (even when only applied topically such as in eyes), and on alkaline phosphatase and thyroid hormone levels. Focal alopecia may develop at site of injection, especially rabies vaccines.

2. PHYSICAL EXAMINATION

Pendulous abdomen and hepatomegaly is frequently seen in hyperadrenocorticism. Enlarged lymph nodes can be seen in leishmaniasis. Abnormal genitalias (e.g., gynecomastia, testicular asymmetry or cryptorchidism) can be observed in hyperoestrogenism.

3. DERMATOLOGIC EXAMINATION

Alopecia may be a feature of a myriad of skin diseases; therefore, thorough clinical examination of hair coat and skin is important. Presence of primary or secondary skin lesions (e.g., papules, pustules, scaling, crusts), follicular casts (e.g., in demodicosis and sebaceous adenitis), skin thickness, aspect of hair shafts (broken or not) are some of the findings that can be very helpful to orient toward more specific diagnoses.

Erythema, papules, pustules, lichenification, self-trauma (recognized by broken hairs and excoriations) are all suggestive of an inflammatory process and pruritus. Thinning of the skin with prominent subcutaneous vessels and calcinosis cutis are pathognomonic of hyperadrenocorticism, whereas hypothyroidism is often accompanied by thickened and hyperpigmented skin without inflammation, unless a secondary bacterial infection is present. In canine recurrent flank alopecia, the alopecic areas are typically well demarcated and hyperpigmented.

COAT AND SKIN COLOUR CHANGE

Coat colour change (e.g., brown discoloration), especially noticeable in white dogs, is suggestive of licking. A regrowth of white hair, where the hair coat was formerly pigmented, is suggestive of alopecia areata.

Intense skin hyperpigmentation of alopecic areas is most commonly seen in dogs with recurrent flank alopecia and alopecia X. However, hyperpigmentation is also often observed in response to chronic inflammation.

PATTERN OF ALOPECIA

The pattern of the hair loss (e.g., focal, multifocal, moth-eaten, asymmetric, symmetric and diffuse) should be documented. Infectious alopecias generally develop a more asymmetric, multifocal, sometimes moth-eaten pattern, whereas endocrine alopecias and other hair cycle abnormalities are more symmetric in pattern. Allergies, however, may also present with bilaterally symmetric alopecia but the history will reveal that the dog demonstrates pruritus toward the affected areas.

Canine pattern alopecia (CPA), as the appellation implies, follows a predetermined distribution and usually start around 6 months of age. In CPA ventral type, the alopecia develops along the ventral neck, chest and abdomen, the caudomedial aspect of thighs, perineum, and the base of the convex aspect of pinnae. In CPA pinnal type, the alopecia involves the entire convex aspect of the pinnae.

4. FURTHER INVESTIGATION

If the results of the above evaluation have failed to produce a definitive diagnosis, further tests are necessary. These should be selected according to the index of suspicion. Microscopic examination of skin scrapings, hair plucks (trichoscopy), Wood’s lamp

examination (+/− fungal culture) and cytological evaluation of impression smears or swabs may all be required if primary or secondary lesions such as papules, pustules, erythema, scaling, crusting, follicular casts are seen.

Haematology, biochemistry and urine analysis may be useful to evaluate the general health status of adult dogs with an alopecic condition or if a systemic disease, which may lead to alopecia, is suspected. Hormonal tests (e.g., thyroid hormone profile, ACTH stimulation test, low dose dexamethasone suppression test) should be carried out if the clinical signs and results of blood or urinalysis suggest an endocrinopathy. In contrast, skin biopsies may be the initial and unique diagnostic procedure performed if sebaceous adenitis is strongly suspected.

REFERENCES

Gortel K. Canine alopecia. Clinical Veterinary advisor 3 rd ed. Elsevier. 2015, pp 47-49.

Mecklenburg L, et al: Hair loss disorders in domestic animals, Ames, IA, 2009, Wiley- Blackwell.

Miller WH Jr, et al: Muller & Kirk’s Small animal dermatology 7 th ed., St. Louis, 2013, Elsevier Saunders.

Paradis M: An approach to symmetrical alopecia in the dog. In Jackson H, Marsella R, editors: BSAVA Manual of canine and feline dermatology, 3 rd ed., Gloucester, UK, 2012, BSAVA, pp 91–102.

Rees C: An approach to canine focal and multifocal alopecia. In Jackson H, Marsella R, editors: BSAVA Manual of canine and feline dermatology 3 rd ed., Gloucester, UK, 2012, BSAVA, pp 86–90.

ALOPECIA, CANINE

Congenital?

Alopecic breeds Acquired • Chinese crested dog Yes No • Mexican hairless dog • Peruvian hairless dog X-linked ectodermal dysplasia Congenital hypotrichosis/alopecia Self-inflicted?

Hypersensitivities Yes No • Atopic dermatitis • Food hypersensitivity • Flea bite hypersensitivity • Parasites (e.g. Sarcoptes )

Focal/multifocal alopecia Symmetric/diffuse alopecia

Cytology, skin scrapings, CBC, chemistry profile, urology, diagnostic trichography, skin biopsy imaging, endocrine evaluation and/or skin biopsy

Infections Endocrinopathies Miscellaneous • Staphylococci • Hypothyroidism • Telogen defluxion • Demodex • Hyperadrenocorticism • Anagen defluxion • Dermatophytes • Hyerestrogenism • Pattern alopecia • Malassezia • Pituitary dwarfism • Pinnal type • Leishmania • Ventral type • Neoplastic alopecia (e.g. epithelitropic lymphoma) Immune-mediated (microscopic inflammation) • Sebaceous adenitis • Dermatomyositis Follicular dysplasias • Post-injection alopecia (rabies vaccine) • Adult-onset generalised ischemic dermatopathy (rabies vaccine-induced or idiopathic) Coat colo ur-linked? • Vasculitis • Alopecia areata (pelade) • Pseudopelade Yes No • Eosinophilic mucinotic mural folliculitis • Granulomatous degenerative mural folliculitis

• Alopecia-X • Recurrent flank alopecia • Colour dilution alopecia • Breed associated follicular dysplasias • Black hair follicular dysplasia • Breed associated follicular dysplasias • Portuguese Water dog • Red or black Doberman f.d. • Irish Water spaniel • Weimaraner’s f.d. • Chesapeake Bay retriever • Rottweiler follicular lipidosis • Pont Audemer spaniel

Adapted from Manon Paradis, Clinical Veterinary Advisor 3rd ed. 2014

HYPOTHYROIDISM –

CUTANEOUS AND NON CUTANEOUS SIGNS

Michael E Herrtage M.A., B.V.Sc., D.V.Sc., D.V.R., D.V.D., D.S.A.M., M.R.C.V.S., Dip. E.C.V.I.M., Dip. E.C.V.D.I. Department of Veterinary Medicine University of Cambridge

Mike Herrtage graduated from the Liverpool University and is currently Professor of Small Animal Medicine at the University of Cambridge and a Fellow of St. Edmund's College, Cambridge. He is Dean of the Cambridge Veterinary School and is in charge of the small animal medicine and diagnostic imaging services at the Queen's Veterinary School Hospital. His clinical responsibilities include all aspects of small animal medicine and diagnostic imaging, but he has a particular interest in endocrine and metabolic disorders. He was awarded the British Small Animal Veterinary Association (B.S.A.V.A.) Woodrow Award in 1986 for outstanding contributions in the field of small animal veterinary medicine and the B.S.A.V.A. Blaine Award for outstanding contributions to the advancement of small animal medicine in 2000. In 2014, he was awarded the World Small Animal Veterinary Association International Award for Scientific Achievement for outstanding contributions by a veterinarian, who has had a significant impact on the advancement of knowledge concerning the cause, detection, cure and/or control of disorders of companion animals. He has been President of the British Veterinary Radiology Association, President of the British Small Animal Veterinary Association, President of the European Society of Veterinary Internal Medicine and President of the European Board of Veterinary Specialisation. He is a Diplomate of both the European College of Veterinary Internal Medicine and of the European College of Veterinary Diagnostic Imaging and was until recently President of the European College of Veterinary Internal Medicine. He has spoken at many international meetings and published over 200 articles in refereed journals.

Hypothyroidism is a multisystemic disorder resulting from inadequate circulating thyroid hormone concentrations. It is considered a common endocrinopathy in the dog and estimates of incidence range from 1 in 156 to 1 in 500 depending on the criteria for diagnosis. However, in the past hypothyroidism may have been overdiagnosed, as the clinical signs are vague and non-specific and diagnostic tests frequently give false positive results in euthyroid dogs. Naturally occurring hypothyroidism is a rare clinical disorder in cats.

Primary hypothyroidism is caused by an intrinsic disorder of the thyroid gland and is the most common type of hypothyroidism in the dog. Hypothyroidism usually results from lymphocytic thyroiditis or thyroid atrophy. Thyroid atrophy may be the end-stage of lymphocytic thyroiditis.

Thyroid neoplasia can occasionally be associated with hypothyroidism, although most dogs with thyroid tumors have normal thyroid function. Congenital hypothyroidism (cretinism) is rare and may be caused by thyroid agenesis, dysgenesis, or dyshormonogenesis. Secondary hypothyroidism is usually associated with pituitary neoplasia, but it may also occur with congenital panhypopituitarism. Hypothalamic dysfunction, iodine deficiency, and serum transport defects are rare causes of hypothyroidism.

Lymphocytic thyroiditis, a presumed autoimmune disorder, accounts for approximately 50% of cases of adult onset hypothyroidism (Graham and others 2007). This autoimmune thyroiditis is likely to arise out of a combination of multiple genetic and environmental factors. It has long been demonstrated that lymphocytic thyroiditis is more prevalent in certain breeds of dog and particularly in familial lines. Familial inheritance has been demonstrated in Borzois, Great Danes, and Beagles.

Lymphocytic thyroiditis is also reported to be highly prevalent in such breeds as Golden retrievers, Cocker spaniels, Boxers, Shetland sheepdogs, Giant Schnauzers and Hovawarts (Graham and others 2007, Ferm and others 2009). For a number of dog breeds, genetic susceptibility to hypothyroidism and lymphocytic thyroiditis is associated with certain haplotypes and alleles of the canine histocompatibility complex (MHC) dog leukocyte antigen (DLA) complex. These include the Doberman pinscher, Rhodesian Ridgeback, English setter, and Giant Schnauzer.

Congenital hypothyroidism has been described in Boxers, Giant Schnauzers, Scottish Deerhounds and Fox terriers.

The most common cause of feline hypothyroidism is iatrogenic destruction or removal of the thyroid gland following radioactive iodine therapy or surgery for the treatment of hyperthyroidism. Spontaneous acquired hypothyroidism has been reported in a cat with lymphocytic thyroiditis. Congenital hypothyroidism has been reported in the cat and may be associated with goiter.

Hypothyroidism may result from dysfunction of any part of the hypothalamic–pituitary– thyroid axis. In lymphocytic thyroiditis there is infiltration of the thyroid gland by lymphocytes, macrophages and plasma cells. Leukocytes and degenerate follicular cells may be found within vacuolated colloid. The parenchyma becomes progressively destroyed and replaced by fibrous connective tissue. In follicular atrophy the parenchyma is replaced by adipose connective tissue. In secondary hypothyroidism the follicular epithelial cells become flattened and the follicles become distended with colloid.

CLINICAL PRESENTATION

The clinical signs of hypothyroidism are very variable and often vague. Some cases present with a classic combination of clinical signs, whereas others may exhibit only one sign. Hypothyroidism usually affects young to middle-aged dogs of the larger breeds. Golden Retrievers, Doberman Pinschers, Boxers, Great Danes and Irish Setters appear to be overrepresented.

Lethargy, mental dullness, bradycardia, poor exercise tolerance, weight gain without an increase in food intake, intolerance to cold, and hypothermia are the most common clinical signs associated with hypothyroidism. Bilaterally symmetrical, nonpruritic alopecia affecting the flanks, thorax, ventral trunk, and neck is associated with inhibition of the hair cycle. The remaining haircoat is dry and dull. The skin is often thickened (myxoedematous) and hyperpigmented. Myxedema of the skin is most evident on the head, resulting in a ‘tragic’ facial expression. The skin, particularly on the ventral abdomen, may be cold and clammy to the touch. Comedones, seborrhoea, and recurrent pyoderma may also be noted. Intact females often have abnormal estrous cycles and reduced fertility. Constipation and corneal lipidosis may occasionally be noted.

Neurological signs may be seen in some dogs with hypothyroidism and include neuromuscular dysfunction with cranial nerve abnormalities, laryngeal paralysis, megaoesophagus, lower motor neuron disease, and encephalopathy. Clinical signs of lameness, dragging of the feet, quadriparesis, hearing impairment, and nystagmus have also been reported. Electromyography may reveal fibrillation potentials and positive sharp waves. Motor nerve conduction velocities may be decreased and tendon reflexes appear sluggish.

Myxedema coma is an extreme form of hypothyroidism with an acute presentation that can prove life-threatening. It is considered to be a complication of chronic hypothyroidism and is manifest by impaired mental status, thermoregulation, respiratory and cardiovascular function.

Affected dogs, mostly Doberman Pinschers, are profoundly dull and present stuporous or comatose with hypothermia in the absence of shivering. The skin can be myxoedematous due to the accumulation of mucopolysaccharides and hyaluronic acid. Bradycardia, hypotension and hypoventilation are also evident.

Congenital hypothyroidism has been reported in a number of breeds including the Boxer and the Giant Schnauzer. Clinical signs of congenital hypothyroidism include hypothermia, lethargy, disproportionate dwarfism with a short, broad skull, short thick limbs and kyphosis, delayed dental eruption, thickened skin, and a dry haircoat. Radiographic changes include delayed epiphyseal ossification and epiphyseal dysgenesis. Growth disturbance gives rise to early onset degenerative joint disease.

Congenital hypothyroidism has also been seen in the cat.

REFERENCES

Graham PA , Refsal KR , Nachreiner RF (2007) Etiopathologic findings of canine hypothyroidism. Vet Clin North Am Small Anim Pract 37(4), 617-31.

Ferm K , Björnerfeldt S , Karlsson A , Andersson G , Nachreiner R , Hedhammar A . (2009) Prevalence of diagnostic characteristics indicating canine autoimmune lymphocytic thyroiditis in giant schnauzer and hovawart dogs. J Small Anim Pract. 50,176-9

LABORATORY TESTS , DRUG INFLUENCES AND

THERAPY OF HYPOTHYROIDISM

Michael E Herrtage M.A., B.V.Sc., D.V.Sc., D.V.R., D.V.D., D.S.A.M., M.R.C.V.S., Dip. E.C.V.I.M., Dip. E.C.V.D.I. Department of Veterinary Medicine University of Cambridge

LABORATORY FINDINGS IN HYPOTHYROIDISM Hypercholesterolemia is found in about 70% of hypothyroid dogs. Thyroid hormones stimulate biliary excretion of cholesterol and a deficiency of these hormones results in an increase in the cholesterol content of the liver. To prevent overloading the liver with cholesterol, the low-density lipoprotein receptors are down-regulated to limit low-density and high-density lipoprotein uptake from the circulation. Plasma concentrations of these lipoproteins rise, causing hypercholesterolaemia. Causes of hypercholesterolemia include: postprandial hyperlipidemia, hypothyroidism, hyperadrenocorticism, diabetes mellitus, cholestatic liver disease, nephrotic syndrome, and primary (idiopathic) hyperlipidaemia

Mild normocytic, normochromic, nonregenerative anaemia occurs in about 30% of hypothyroid dogs and represents a physiological response to the lowered basal metabolic rate.

Mild to moderate increases in serum activity of ALT, AST, AP, and CK may be noted. Increased CK activity is particularly associated with myopathy in cases of hypothyroidism.

THYROID FUNCTION TESTS

SERUM TOTAL AND FREE T4

Baseline serum T4 concentration using a validated assay is more accurate than serum T3 in assessing the status of thyroid gland function and is recommended for initial evaluation of the thyroid gland. Random fluctuations in serum T4 concentrations occur, but a true circadian rhythm has not been identified.

Serum T4 concentrations can be affected by breed, age, illness, and drug administration. Certain breeds, particularly sighthounds, have lower serum T4 concentrations than other breeds and this is important when interpreting results from Greyhounds or Afghan Hounds, for example. Serum T4 concentrations tend to be higher in young growing puppies and lower in old dogs when compared with normal adult concentrations. Concurrent illness can suppress serum thyroid hormone concentrations (sick euthyroid syndrome). The degree of suppression is dependent on the severity of the illness or catabolic state rather than the specific disorder. Various drugs can alter thyroid hormone metabolism and serum binding, particularly glucocorticoids, anticonvulsants, NSAIDs, potentiated sulphonamides, furosemide, and anaesthetic agents.

Serum free T4 concentrations measure metabolically active T4 and should not be influenced by the effects of serum binding. However, measurement of serum free T4 by most assays, which do not employ equilibrium dialysis, has not proved to be any more reliable than total T4 concentrations in the diagnosis of hypothyroidism. Serum free T4 measured by equilibrium dialysis can prove useful in differentiating genuine hypothyroidism when the total T4 concentration is in reference range.

A low basal serum T4 concentration, with a history and clinical signs compatible with hypothyroidism, may be sufficient evidence to warrant a therapeutic trial. In one study the predictive value of a positive test result was 0.75 and of a negative test result was 0.87 using T4 concentrations to diagnose hypothyroidism. Serum T4 concentrations in the low normal or nondiagnostic range should have further tests performed (e.g. a canine TSH concentration and/or a TSH or TRH stimulation test) provided the index of suspicion is still high for hypothyroidism.

Serum T4 concentrations in the normal range are unlikely to be associated with hypothyroidism. However, antibodies to thyroid hormone can cause discordance between measured thyroid hormone concentrations and the clinical status of the dog. Depending on their concentration, binding affinity, and the assay method employed, thyroid antibodies can result in either falsely elevated or falsely low thyroid hormone concentrations. Autoantibodies to T4 and T3 can be measured in these cases.

SERUM TOTAL T3 AND FREE T3

Baseline serum T3 concentrations are less accurate for predicting hypothyroidism than serum T4. Random fluctuations in serum T3 concentrations are greater than with serum T4 and have a greater tendency to be misleading with respect to the status of thyroid gland function. Possible explanations for this discrepancy include the normal thyroid gland’s preference for secreting T4, the intracellular formation and location of most T3, the preferential secretion of T3 compared with T4 as thyroid function progressively fails, and the development of anti-T3 antibodies. The diagnostic value of serum T3 concentrations in hypothyroidism is therefore inferior to serum T4.

ENDOGENOUS CANINE TSH

Measurement of canine TSH (c-TSH) has revolutionised the testing of hypothyroidism, particularly in primary hypothyroidism where the concentrations should be high because of loss of the negative feedback effect of thyroid hormones. A validated c-TSH assay is now widely available, but unfortunately it has shown that not all cases of primary hypothyroidism exhibit elevated c-TSH concentrations and that some euthyroid dogs as well as some dogs with nonthyroidal illness may have elevated TSH concentrations. The general conclusions are that c-TSH measurements are useful when measured together with serum total T4 concentrations in the diagnosis of cases of suspected hypothyroidism, however the sensitivity and specificity of the assay particularly at lower concentrations are insufficient to obviate the need for a dynamic test (TSH or TRH stimulation test) to confirm the diagnosis in some cases of hypothyroidism.

TSH STIMULATION TEST

The administration of exogenous TSH to measure thyroid secretory reserve used to be considered the gold standard for the diagnosis of hypothyroidism. Unfortunately, pharmaceutical grade bovine TSH is no longer available, but more recently recombinant human TSH has become available. The protocol and interpretation criteria are given below. The use of this test is limited by the expense of the TSH injection.

Peak serum T4 responses are decreased by nonthyroidal illness and drug administration in the same way as basal T4 concentrations. Thyroid function testing is thus best performed after resolution of nonthyroidal illness and, if possible, with the patient off all medication.

TSH STIMULATION TEST

Protocol : Collect plasma or serum sample for basal T4 concentration. Administer 50–75 µg/dog recombinant human TSH intravenously. Collect second sample for T4 concentration six hours later.

Interpretation : A diagnosis of primary hypothyroidism can be confirmed if both the pre- and post- T4 samples are below the reference range for basal T4 concentration. In normal animals the T4 concentration should be stimulated to well within or above the normal reference range for T4. In most animals the T4 concentration should increase by at least 1.5 times the basal concentration. Interpretation of intermediate results is more difficult and may occur in association with nonthyroid illness, treatment with certain drugs, secondary hypothyroidism, or possibly in the early stages of primary hypothyroidism.

TRH STIMULATION TEST

TRH is more readily available and less expensive than TSH. However, the T4 response to TRH is less predictable and peak concentrations tend to be lower than with TSH stimulation. Increasing the dose of TRH (above 200 µg/dog) increases the duration but not the magnitude of the T4 response. TRH administration may cause cholinergic signs such as salivation, vomiting, and defecation. Responses are also affected by nonthyroidal illness and drug administration.

REVERSE T3 (RT3)

The measurement of serum rT3 concentration can be useful in identifying cases with significant nonthyroidal illness and should be reserved for those cases with discordant or equivocal T4 concentrations. If the serum rT3 concentration is high in a dog with low or low-normal T4, hypothyroidism is unlikely to be the cause of the animal’s clinical signs.

THYROGLOBULIN AUTOANTIBODIES (TGAA)

Lymphocytic thyroiditis is a major cause of canine hypothyroidism and, as part of the inflammatory process, antibodies to thyroid antigens are released into the circulation. Thyroglobulin is the principal antigen for which measurable serum antibodies are present. Therefore, measurement of TgAA provides evidence of an active inflammatory process in the the thyroid gland. However, the presence of TgAA does not provide information about thyroid function, since at least 60–70% of the gland has to be destroyed before thyroid dysfunction occurs. Consequently, both lymphocytic thyroiditis and TgAA can be found in dogs that are not hypothyroid and, in dogs where hypothyroidism is caused by thyroid atrophy, circulating TgAA may not be present at all.

THYROID BIOPSY

Although not commonly performed, the histologic examination of a thyroid gland biopsy provides an accurate method of differentiating between primary and secondary hypothyroidism. In primary hypothyroidism there is loss of thyroid follicles resulting from either lymphocytic thyroiditis or thyroid atrophy. In secondary hypothyroidism the thyroid follicles become distended with colloid and the follicular epithelial cells are flattened. Testing thyroid function is still required to make a diagnosis of hypothyroidism, since the degree of histologic change does not always relate to reduced hormone production and release.

MANAGEMENT OF HYPOTHYROIDISM

Thyroid hormone replacement is required for the treatment of hypothyroidism. Synthetic forms of T4 and T3 are available. Sodium levothyroxine (l-thyroxine) is the treatment of choice because it most closely resembles the preferential secretion of T4 by the normal thyroid gland. Synthetic T4 is readily deiodinated to T3 in peripheral tissues and therefore does not bypass the normal cellular regulatory processes that control the production of the more potent T3 in those tissues.

An initial replacement dose of l-thyroxine is 20–40 µg/kg daily in divided doses. Although it has been suggested that once daily dosing is sufficient in many cases, the author has documented a number of cases where once daily administration has failed to maintain adequate serum concentrations throughout the day, with a consequent failure of the clinical signs to resolve fully. Poor absorption and a shorter half-life for T4 explain why dogs require higher doses and more frequent administration than human patients with hypothyroidism.

Therapy should always be continued for a minimum of three months. Improved activity and mental alertness are usually seen within two weeks, but skin and haircoat changes may take up to six months to resolve.

The effect of treatment can be monitored by measurement of post-pill serum T4 concentrations. Sampling 4–6 hours after dosing will give a peak serum T4 concentration and a sample taken just prior to dosing will give the lowest serum T4 concentration. The dose and frequency of administration should be adjusted to maintain the serum T4

concentration in the high end of the reference range throughout the day. Underdosage may lead to treatment failure and overdosage can lead to iatrogenic hyperthyroidism. Replacement therapy is required for life.

Possible causes for cases failing to respond to replacement therapy include misdiagnosis, inadequate dose or frequency of administration, poor GI absorption, and peripheral tissue resistance.

Congenital hypothyroidism should be treated as early as possible to achieve normal growth and development. The dose will require adjustment as the patient grows and gets older, so post-pill assessments are required at monthly intervals during the first year of life.

HYPERADRENOCORTICISM – CUTANEOUS AND

ON UTANEOUS IGNS N C S

Michael E Herrtage M.A., B.V.Sc., D.V.Sc., D.V.R., D.V.D., D.S.A.M., M.R.C.V.S., Dip. E.C.V.I.M., Dip. E.C.V.D.I. Department of Veterinary Medicine University of Cambridge

Hyperadrenocorticism is the excessive production or administration of glucocorticoids and is one of the most commonly diagnosed endocrinopathies in the dog. Hyperadrenocorticism is rare in the cat.

SIGNALMENT

Pituitary-dependent hyperadrenocorticism is usually a disease of the middle-aged to older dog, with an age range of 2 to 16 years and reported median ages of 7 to 9 years. Dogs with adrenal-dependent hyperadrenocorticism tend to be older ranging between 6 and 16 years with mean age reported as 11.3 years (Reusch and Feldman, 1991).

Any breed can develop hyperadrenocorticism but poodles, dachshunds and small terriers, for example the Yorkshire terrier, Jack Russell terrier and Staffordshire bull terrier, appear more at risk at developing pituitary-dependent hyperadrenocorticism. Adrenocortical tumours occur more frequently in larger breeds with about 50 per cent of dogs weighing greater than 20 kg (Reusch and Feldman, 1991).

There is no significant difference in sex distribution in pituitary-dependent hyperadrenocorticism. However, in one survey, between 60 and 65 per cent of dogs with functional adrenocortical tumours were female (Reusch and Feldman, 1991).

CAUSES OF HYPERADRENOCORTICISM

Hyperadrenocorticism can be spontaneous or iatrogenic. Spontaneously occurring hyperadrenocorticism may be associated with inappropriate secretion of ACTH by the pituitary (pituitary-dependent hyperadrenocorticism) or associated with a primary adrenal disorder (adrenal-dependent hyperadrenocorticism).

PITUITARY-DEPENDENT HYPERADRENOCORTICISM

Pituitary-dependent hyperadrenocorticism accounts for over 80 per cent of dogs with naturally occurring hyperadrenocorticism. Excessive ACTH secretion results in bilateral adrenocortical hyperplasia and excess cortisol secretion. There is a failure of the negative

feedback mechanism of cortisol on ACTH. However ACTH secretion may remain episodic resulting in fluctuating cortisol concentrations, which may at times fall within the reference range.

More than 90 per cent of dogs with pituitary-dependent hyperadrenocorticism have a pituitary tumour. Adenomas of the corticotropic cells of the pars distalis and pars intermedia are the most common type of canine pituitary tumour reported. Most of these pituitary tumours are microadenomas (less than 10 mm in diameter). Detection of such small tumours requires careful microdissection, experience and special stains.

In one study using immunocytochemical staining, more than 80 per cent of dogs with pituitary-dependent hyperadrenocorticism were positive for pituitary adenomas (Peterson et al., 1982a). Macroadenomas (greater than 10 mm diameter) are seen in about 10 to 15 per cent of dogs (Duesberg et al., 1995). These may compress the remaining pituitary gland and extend dorsally into the hypothalamus. However, they are generally slow growing and may not produce neurological signs. Corticotropic adenocarcinomas have been reported but are rare.

From a clinical point of view the precise pituitary pathology is not of great importance unless neurological signs are present at the time of diagnosis or if they become apparent during the initial treatment.

ADRENAL-DEPENDENT HYPERADRENOCORTICISM

The remaining 15 to 20 per cent of spontaneous cases of hyperadrenocorticism are caused by unilateral or, occasionally bilateral, adrenal tumours. Adrenocortical tumours may be benign or malignant, although it can be difficult histologically to distinguish between an adrenocortical adenoma and a carcinoma unless there is evidence of invasion or metastasis. The benign tumours are usually small and well-circumscribed tumours but are commonly partly calcified (Reusch and Feldman, 1991). In contrast adrenocortical carcinomas are usually large, locally invasive, haemorrhagic and necrotic. They are also often calcified. Carcinomas, especially of the right adrenal, frequently invade the phrenicoabdominal vein and caudal vena cava and metastasize to the liver, lung and kidney.

In dogs, adrenocortical adenomas and carcinomas occur with approximately equal frequency. The cortex contiguous to the tumour and that of the contralateral gland atrophy in the presence of functional adenomas and carcinomas.

OTHER POTENTIAL CAUSES OF HYPERADRENOCORTICISM

There are also a few reports of dogs with pituitary-dependent hyperadrenocorticism having concurrent adrenal tumours (Greco et al., 1999). Bilateral adrenal tumours have also been reported, but appear to be rare (Ford et al, 1993). Ectopic ACTH production would appear to be very rare cause of hyperadrenocorticism in the dog with only one suspected case reported (Galac et al. 2003).

CLINICAL SIGNS

Affected dogs usually develop a classic combination of clinical signs associated with increased glucocorticoid concentrations and these are listed in approximate decreasing order of frequency. Larger breeds of dogs and those with recent onset of disease, however, may only show a few characteristic signs rather than the classic array of clinical signs usually observed in smaller breeds.

Hyperadrenocorticism has an insidious onset and is slowly progressive over many months or even years. Many owners consider the early signs (e.g. alopecia, lethargy) as part of the normal ageing process of their dog or misinterpret the signs (e.g. increased appetite) as those of good health. In a few cases, clinical signs may be intermittent, with periods of remission and relapse and in others there may be an apparent rapid onset and progression of clinical signs.

POLYDIPSIA AND POLYURIA

Polydipsia, defined as water intake in excess of 80 ml/kg body weight/day and polyuria, defined as urine production in excess of 40 ml/kg body weight/day, are noted in nearly all cases of hyperadrenocorticism. Excessive thirst, nocturia, incontinence and/or urination in the house are usually reported by owners. The precise cause of the polyuria remains obscure, but may be due to increased glomerular filtration rate, inhibition of the release of antidiuretic hormone (ADH), inhibition of the action of ADH on the renal tubules or possibly accelerated inactivation of ADH. The end result is a partial secondary nephrogenic diabetes insipidus. The polydipsia occurs secondary to the polyuria. Dogs with macroadenomas may show signs of concurrent central diabetes insipidus due to compression of the posterior lobe of the pituitary and hypothalamus.

POLYPHAGIA AND WEIGHT GAIN

Although increased appetite is a common sign, many owners dismiss it as a sign of good health. A voracious appetite, scavenging or stealing food, however, may give rise to concern especially if the dog previously had a poor appetite. Polyphagia is assumed to be a direct effect of glucocorticoids on the brain but there is little actual evidence to support this theory.

Hyperadrenocorticism is also associated with an increase in weight in most cases despite a concurrent loss of muscle mass. The weight gain is only partly due to the polyphagia as even dogs fed maintenance rations may gain weight if they develop HAC. Cortisol also has effects on fat distribution so the increased fat deposits tend to occur over the dorsum and within the abdomen. This gives affected dogs the typical ‘table top’ appearance when viewed from above.

ABDOMINAL DISTENSION

A pot-bellied appearance is very common in hyperadrenocorticism but may develop so slowly that owners fail to recognise its significance. Abdominal distension is associated with

the redistribution of fat to the abdomen, liver enlargement and weakness of the abdominal muscles. The weakness of the abdominal muscles makes palpation of the pendulous abdomen easier and more rewarding.

MUSCLE WASTING / WEAKNESS

The gradual onset of lethargy and poor exercise tolerance is initially considered by most owners to be compatible with ageing. Owner may only become concerned when muscle weakness leads to an inability to climb stairs or jump into a car. Lethargy, excessive panting and poor exercise tolerance are probably an expression of muscle wasting and weakness. Apart from the development of a pendulous abdomen, decreased muscle mass may be noted around the limbs, over the spine or over the temporal region. Muscle weakness is the result of muscle wasting caused by protein catabolism and a direct effect of cortisol on cell membrane excitability.

MYOTONIA

Occasionally, dogs with hyperadrenocorticism develop myotonia, characterised by persistent active muscle contractions that continue after voluntary or involuntary stimuli. The condition seems especially prevalent in the miniature Poodle. All limbs may be affected, but the signs are usually more severe in the hindlegs. The animals with myotonia walk with a stiff stilted gait or rabbit hop. The affected limbs are rigid and rapidly return to extension after being passively flexed. In some cases passive flexion may be difficult or impossible to achieve because of the persistent muscle tone. Spinal reflexes are difficult to elicit because of the rigidity, but pain sensation is normal. The muscles are usually slightly hypertrophied rather than being atrophied and a myotonic dimple can be elicited by percussion of the affected muscle.

Bizarre high frequency discharges are noted on electromyography (Duncan et al., 1977). These bizarre myotonic and pseudomyotonic discharges may be found in some dogs with hyperadrenocorticism that do not show obvious clinical manifestations of myotonia.

DERMATOLOGICAL FEATURES

The skin, particularly over the ventral abdomen, becomes thin and inelastic because of atrophy of the skin connective tissues. Elasticity can be assessed clinically by tenting the skin between the thumb and forefinger. In the normal dog the skin will flow back to a smooth contour but in hyperadrenocorticism it remains tented. Striae (skin wrinkles) can form as a result of this inelasticity. The abdominal veins are prominent and easily visible through the thin skin. There is often excessive surface scale, and comedomes caused by follicular plugging are seen, especially around the nipples. Hyperpigmentation of the skin is rare in canine hyperadrenocorticism.

Thinning of the haircoat leading to bilaterally symmetric alopecia is frequently seen with hyperadrenocorticism and occurs because of the inhibitory effect of cortisol on the anagen or growth phase of the hair cycle. The remaining hair is dull and dry because it is in the telogen or resting phase of the hair cycle. The alopecia is non-pruritic and affects mainly

the flanks, ventral abdomen and chest, perineum and neck. The head, feet and in some cases the tail are usually the last areas to be affected. The coat colour is often lighter than normal. Occasionally affected dogs may not lose their haircoat, but retain it becoming hypertrichotic. When hair has been clipped in dogs with hyperadrenocorticism, it will frequently fail to re-grow or the re-growth will be poor or sparse.

Protein catabolism causing atrophy of the skin collagen also leads to excessive bruising following venepuncture or other minor trauma. Wound healing is extraordinarily slow, presumably because of inhibition of fibroblast proliferation and collagen synthesis. Healing wounds often undergo dehiscence and even old scars may start to breakdown. Bruising at the sites of venepuncture is common.

Calcinosis cutis is a frequent finding in biopsy material from the skin, however clinical evidence of calcinosis cutis is less common. The gross appearance can vary but the predeliction sites are the neck, axilla, ventral abdomen and inguinal areas. Calcinosis cutis usually appears as a firm, slightly elevated, white or cream plaque surrounded by a rim of erythema. Large plaques tend to crack, become secondarily infected and develop a crust containing white powdery material. The exact pathogenesis is unknown but parathyroid hormone concentrations are increased and this may lead to increased calcium mobilisation from skeletal reserves followed by soft tissue calcification. Plasma calcium and phosphate concentrations are usually normal.

ANOESTRUS / TESTICULAR ATROPHY

Entire bitches with hyperadrenocorticism usually cease regular oestrus cycles. The length of anoestrus, often years, indicates the duration of the disease process. In the intact male both testes become soft and spongy. Anoestrus and testicular atrophy occur due to the negative feedback effect of high concentrations of cortisol on the pituitary, which also suppress secretion of gonadotropic hormones.

NEUROLOGICAL SIGNS

Although uncommon at the time of presentation, a few cases will develop neurological signs associated with a large functional pituitary tumour. The size of the tumour is a less important factor that its rate of growth in determining the effects of a pituitary mass. The most common clinical signs are dullness, depression, disorientation, loss of learned behaviour, anorexia, aimless wandering or pacing, head pressing, circling, ataxia, blindness, anisocoria and seizures. More often, however, neurological signs develop during initial treatment of pituitary-dependent hyperadrenocorticism with trilostane or mitotane. This is thought to involve removal of the negative feedback inhibition of cortisol on the pituitary and hypothalamus, which then allows some pituitary tumours to enlarge rapidly, resulting in oedema and increased intracranial pressure.

Intracranial haemorrhage from the pituitary tumour may lead to pituitary apoplexy, which is characterised by a acute severe depression and diabetes insipidus that is often, though not universally, fatal (Long and others 2003). Trigger factors for pituitary apoplexy are not known in dogs but in humans there is an association with recent endocrine testing.

HYPERTENSION

Systemic hypertension occurs in over 50 per cent of dogs with untreated hyperadrenocorticism. The mechanisms underlying the hypertension have been suggested as an excessive secretion of renin, activation of the renin-angiotensin system, enhanced vascular sensitivity to catecholamines and a reduction of vasodilator prostaglandins (Goy- Thollot et al, 2002). In the majority of cases, the moderate degree of hypertension is not associated with clinical signs, but hypertension-induced blindness due to intraocular haemorrhage and retinal detachment has been reported. Hypertension may also exacerbate left ventricular hypertrophy and congestive heart failure and cause glomerular damage and proteinuria. In general hypertension does not resolve with therapy.

ROUTINE LABORATORY FINDINGS

HAEMATOLOGY

The most consistent haematological finding is a stress leucogram with a relative and absolute lymphopenia (< 1.5 x 10 9/l) and eosinopenia (< 0.2 x 10 9/l). Lymphopenia is most likely the result of steroid lymphocytolysis and eosinopenia results from bone marrow sequestration of eosinophils. A mild to moderate neutrophilia and monocytosis may be found and is thought to result from decreased capillary margination and diapedesis associated with excess glucocorticoids.

The red cell count is usually normal, although mild polycythaemia may occasionally be noted. Platelet counts may also be increased. These findings are thought to result from stimulatory effects of glucocorticoids on the bone marrow.

BIOCHEMISTRY

ALKALINE PHOSPHATASE

Serum alkaline phosphatase (ALP) concentrations are increased in over 90 per cent of cases of canine hyperadrenocorticism. The increase in serum ALP concentration is commonly 5 to 40 times the upper end of the reference range and is perhaps the most sensitive biochemical screening test for hyperadrenocorticism. However it is also perhaps the most non-specific. The increased concentration occurs because glucocorticoids, both endogenous or exogenous, induce a specific hepatic isoenzyme of ALP, which is unique to the dog. A normal serum ALP concentration does not exclude a diagnosis of hyperadrenocorticism and increases in serum ALP due to other conditions should always be considered.

Measurement of the glucocorticoid-induced isoenzyme of ALP is a test that is quite sensitive, but non-specific, for spontaneous canine hyperadrenocorticism as the glucocorticoid-induced isoenzyme can be increased in primary hepatopathies, diabetes mellitus, and in dogs treated with anticonvulsants and glucocorticoids (Teske et al., 1989).

ALANINE AMINOTRANSFERASE

Alanine aminotransferase (ALT) is commonly increased in hyperadrenocorticism, but the increase is usually only mild and is believed to result from liver damage caused by swollen hepatocytes due to glycogen accumulation.

GLUCOSE

Blood glucose is usually in the high reference range. About 10 per cent of cases develop overt diabetes mellitus, which is caused by antagonism to the action of insulin by the gluconeogenic effects of excess glucocorticoids.

UREA AND CREATININE

Blood urea concentration is usually normal to decreased due to the continual urinary loss associated with glucocorticoid-induced diuresis. Serum creatinine concentration also tends to be at the low end of the reference range. Urea and concentrations at the high end of the reference range are therefore of some concern in cases of HAC and may become overtly azotaemic when treatment for the hyperadrenocorticism is started.

CHOLESTEROL AND TRIGLYCERIDE

Cholesterol is usually greater than 8 mmol/l but this is not a specific finding as cholesterol is also raised in hypothyroidism, diabetes mellitus, cholestatic liver disease and protein- losing nephropathy, all of which may be differential diagnoses. Hypertriglyceridaemia can also occur although less frequently. It can interfere with the accurate assessment of a number of other laboratory parameters.

ELECTROLYTES

Serum sodium, potassium, calcium and phosphorus concentrations are usually within the reference range. However phosphate concentrations may be increased when compared to age matched controls (Ramsey and others 2005).

BILE ACIDS

Resting and post-prandial serum bile acid concentrations may show a mild to moderate elevation in some cases of hyperadrenocorticism due to steroid hepatopathy. When abnormal results are obtained, it may prove difficult to differentiate hyperadrenocorticism from primary liver disorders. The patient’s appetite, thirst, weight changes and other clinical signs are useful in making this distinction.

URINALYSIS

URINE SPECIFIC GRAVITY

The specific gravity of urine is usually less than 1.015 and is often hyposthenuric (<1.008) provided water has not been withheld. Dogs with hyperadrenocorticism can usually concentrate their urine if water is deprived, but their concentrating ability is frequently reduced. However, in some cases of pituitary-dependent hyperadrenocorticism with a macroadenoma, compression of the posterior lobe of the pituitary and suprasellar extension into the hypothalamus may cause disruption to antidiuretic hormone production and release and signs of central diabetes insipidus.

URINARY TRACT INFECTION

Urinary tract infections occur in about 50 per cent of cases of hyperadrenocorticism because urine is retained in an over distended bladder due to incomplete voiding caused by muscle weakness. There is often little evidence of blood, or inflammatory cells in the sediment of the urine and indeed few clinical signs of urinary tract infection due to the immunosuppressive action of excess glucocorticoids. Therefore culture of urine samples obtained by cystocentesis is required to demonstrate the infection. Urinary tract infections can also ascend to the kidneys to cause pyelonephritis.

URINE PROTEIN

Up to 45 per cent of dogs with untreated hyperadrenocorticism have proteinuria, defined as a urine protein:creatinine ratio greater than 1.0, in the absence of urinary tract infection (Hurley and Vaden, 1998). The proteinuria is usually mild and associated with systemic hypertension.

URINE GLUCOSE

Glycosuria is present in the 10 per cent of cases with overt diabetes mellitus.

EFFECTS ON OTHER ENDOCRINE RESULTS

THYROID FUNCTION TESTS

Serum total thyroxine (T4) and/or triiodothyronine (T3) concentrations are decreased in about 70 per cent of dogs with hyperadrenocorticism (Peterson et al., 1984). Over 60 per cent of dogs with low serum total T4 concentrations, also have low free T4 concentrations (Ferguson and Peterson 1992). The response of thyroxine to TRH or TSH stimulation usually parallels a normal response, but thyroxine concentrations both pre- and post- TRH or TSH are subnormal. These effects are thought to be due to inhibition of pituitary secretion of thyrotropin (thyroid-stimulating hormone, TSH) and a blunted TSH response to TRH stimulation (Ramsey and Herrtage, 1998). However, the situation is more complex than this, since in some cases of spontaneous hyperadrenocorticism canine TSH

concentrations may be normal or even increased. The cause for this is not known, but may be due to excess cortisol altering thyroid hormone binding to plasma proteins or enhancing the metabolism of thyroid hormone. In one study, an increased free T4 fraction indicative of reduced serum T4 binding was identified in nearly 40 per cent of dogs with hyperadrenocorticism (Ferguson and Peterson, 1992).

PARATHYROID HORMONE

Glucocorticoids are known to increase urinary calcium excretion in canine hyperadrenocorticism. In order to maintain normal circulating concentrations of calcium, parathormone (PTH) concentrations are increased in over 80 per cent of cases of hyperadrenocorticism (Ramsey and others, 2005). PTH concentrations appear to become raised early in the course of the disease in both pituitary and adrenal-dependent hyperadrenocorticism.

GROWTH HORMONE AND INSULIN-LIKE GROWTH FACTOR 1

Chronic glucocorticoid excess reduces spontaneous and stimulated GH secretion by enhanced release of somatostatin from the hypothalamus. Reduced GH secretion from the pituitary may result in reduced serum IGF-1 concentrations.

INSULIN AND C-PEPTIDE

It has been shown that both insulin and C-peptide (which is released in equimolar concentrations to insulin) concentrations are increased in dogs with hyperadrenocorticism and that their response to glucagon is exaggerated when compared to healthy dogs (Montgomery and others, 1996). Peripheral insulin resistance produced by cortisol explains this observation and ultimately may result in overt diabetes mellitus.

REFERENCES please see page 44

YPERADRENOCORTICISM H –

DIAGNOSIS AND TREATMENT

Michael E Herrtage M.A., B.V.Sc., D.V.Sc., D.V.R., D.V.D., D.S.A.M., M.R.C.V.S., Dip. E.C.V.I.M., Dip. E.C.V.D.I. Department of Veterinary Medicine University of Cambridge

ENDOCRINE SCREENING TESTS

A presumptive diagnosis of hyperadrenocorticism can be made from clinical signs, physical examination, routine laboratory tests and diagnostic imaging findings, but the diagnosis must be confirmed by hormonal assay. A single resting or basal plasma or serum cortisol determination is of very limited diagnostic value because of the overlap in cortisol concentrations obtained from normal and abnormal disease states. The most commonly used screening tests are the ACTH stimulation test or the low-dose dexamethasone suppression test, however, the urinary corticoid: creatinine ratio has also proved a useful screening test. None of these tests are perfect and all are capable of giving false negative and false positive test results.

If a dog with clinical signs compatible with hyperadrenocorticism produces a negative result with one screening test, an alternative screening test should be used. False positive results can be obtained in dogs suffering from non-adrenal disease (Kaplan et al., 1995). A definitive diagnosis of hyperadrenocorticism should never be made purely on the basis of results of any of these screening tests, especially in dogs without classic signs of hyperadrenocorticism or in dogs with known non-adrenal disease.

The relative merits of each test and interpretation are discussed below. The authors’ preference is to use the ACTH stimulation test as the first screening test and the low-dose dexamethasone suppression test if the ACTH stimulation test gives a normal result in a dog with clinical signs suspicious of hyperadrenocorticism.

ACTH STIMULATION TEST

The ACTH stimulation test is the best screening test for distinguishing spontaneous from iatrogenic hyperadrenocorticism. In spontaneous hyperadrenocorticism, the ACTH stimulation test reliably identifies more than 50 per cent of dogs with adrenal-dependent hyperadrenocorticism and about 85 per cent of dogs with pituitary-dependent hyperadrenocorticism. Occasional false positive results do occur; however false negative results are more common.

It is a simple, robust and quick test to perform and documents excessive production of glucocorticoids by the adrenal cortex in cases of hyperadrenocorticism. The information gained is also useful in providing baseline information for monitoring trilostane or mitotane therapy, although different criteria are used to interpret cortisol results during treatment. The cost of ACTH varies considerably and this limits the use of this test in some countries.

The ACTH stimulation test does not however, reliably differentiate adrenal-dependent from pituitary-dependent hyperadrenocorticism. A diagnosis of hyperadrenocorticism should not by excluded on the basis of a normal ACTH response if the clinical signs are compatible with the disease.

Occasionally, an animal under chronic stress may develop some degree of adrenal hyperplasia, which produces an abnormal ACTH response. This may be seen for example with diabetes mellitus or pyometra and a normal cortisol response to ACTH stimulation will be obtained after treatment of the underlying disease in these cases.

It is essential to use absolute values for pre- and post- ACTH plasma cortisol concentrations rather than a ratio or percentage increase in post-ACTH cortisol concentration over the basal concentration. In normal dogs, pre- ACTH cortisol concentrations are usually between 20 and 250 nmol/l with post- ACTH cortisol concentrations between 200 to 450 nmol/l. Regardless of the pre-ACTH cortisol value, a diagnosis of hyperadrenocorticism can be confirmed by demonstrating a post-ACTH cortisol concentration greater than 600 nmol/l in dogs with compatible clinical signs and without evidence of concurrent non-adrenal disease.

LOW-DOSE DEXAMETHASONE SUPPRESSION TEST

The low-dose dexamethasone suppression test is more reliable than the ACTH stimulation test in confirming hyperadrenocorticism, since the results are diagnostic in the majority of adrenal-dependent cases and in 90 to 95 per cent of dogs with pituitary-dependent hyperadrenocorticism. Occasional false negative results do occur; however false positive results are more common.

The low-dose dexamethasone suppression test is not as accurate as the ACTH stimulation test for the detection of iatrogenic hyperadrenocorticism. The test is also affected by more variables than the ACTH stimulation test, takes 8 hours to complete and does not provide pre-treatment information that may used in monitoring the effects of mitotane or trilostane therapy. The low-dose dexamethasone suppression test does not reliably differentiate pituitary-dependent from adrenal-dependent hyperadrenocorticism.

Interpretation of the results of a low-dose dexamethasone suppression test must be based on the laboratory's reference range for the dose and preparation of dexamethasone administered. If the dose of dexamethasone fails to adequately suppress circulating cortisol concentrations in a dog with compatible clinical signs, a diagnosis of hyperadrenocorticism is confirmed.

While basal and 8-hour post-dexamethasone samples are most important for interpretation of the test, one or more samples taken at intermediate times (for example, 2, 4, or 6 hours) during the test period may also prove helpful. If a plasma cortisol concentration

determined 2 - 6 hours after dexamethasone injection is suppressed normally or near- normally (to below approximately 40 mmol/l), while the 8-hour sample shows escape from cortisol suppression, then a diagnosis of pituitary-dependent hyperadrenocorticism can be made. If the cortisol is not suppressed by the dexamethasone at all then the cause of the hyperadrenocorticism cannot be determined. A few dogs with HAC confirmed by other methods may show an ‘inverse’ pattern of results i.e. a failure of suppression at 4 hours but suppression at 8 hours (Mueller and others, 2006). As the 4 hour result is not normal, these dogs cannot be described as false negatives. The importance and reliability of this pattern has still to be determined.

URINARY CORTICOID: CREATININE RATIO

Evaluation of urinary corticoid:creatinine ratio rather than the more laborious 24-hour urinary corticoid excretion has been shown to be a simple and valuable screening test for hyperadrenocorticism (Rijnberk et al., 1988).

Cortisol and its metabolites are excreted in urine. By measuring urinary corticoids in the morning sample, the concentration will reflect cortisol release over a period of several hours, thereby adjusting for fluctuations in plasma cortisol concentrations. Relating the urine corticoid concentration to urine creatinine concentration provides a correction for any differences in urine concentration.

Urine is collected in the morning for cortisol and creatinine estimations. It is preferable for the dog to be at home for this test so that the dog is subjected to as little stress as possible otherwise abnormal cortisol concentrations will be found in the urine. The urine cortisol: creatinine ratio is determined by dividing the urine cortisol concentration (in µmol/l) by the urine creatinine concentration (in µmol/l).

The reference ratio for normal dogs is less than 10 x10 -6. The urine corticoid:creatinine ratio is increased above the normal (> 10 x 10 -6) in dogs with hyperadrenocorticism. However the ratio is also increased in many dogs with non-adrenal illness (Smiley and Peterson 1993). Therefore while this simple test appears highly sensitive in detecting hyperadrenocorticism in dogs, it is not that specific.

The test does provide a good screening test for hyperadrenocorticism in that values in the reference range make a diagnosis of hyperadrenocorticism highly unlikely. The urine corticoid:creatinine ratio does not reliably differentiate pituitary-dependent from adrenal- dependent hyperadrenocorticism unless the ratio exceeds 100 x 10 -6, when it becomes very likely that the dog is suffering from pituitary-dependent hyperadrenocorticism (Galac et al., 1997).

The test is of little value in monitoring the response to mitotane or trilostane therapy in dogs with hyperadrenocorticism (Guptill et al., 1997; Galac and others, 2009).

TESTS TO DIFFERENTIATE THE CAUSE OF HYPERADRENOCORTICISM

The ability to differentiate between pituitary- and adrenal-dependent hyperadrenocorticism can have important implications in providing the most effective method of management for the disease. An accurate test is therefore required to differentiate pituitary from adrenal causes of hyperadrenocorticism. The high-dose dexamethasone suppression test used to be the most commonly used test for differentiating the cause of hyperadrenocorticism, but its accuracy has recently been brought into question. Canine ACTH assays are now readily available and the determination of the plasma ACTH concentration has been shown to provide reliable discrimination between pituitary and adrenal causes of hyperadrenocorticism (Gould et al., 2001).

Diagnostic imaging techniques, particularly abdominal ultrasonography, have also proved sensitive in distinguishing dogs with pituitary-dependent hyperadrenocorticism from dogs with adrenocortical tumours. Recognition of metastatic lesions with radiography and/or ultrasonography, however, is the only method that can reliably distinguish dogs with adenomas from dogs with carcinomas in the absence of histopathology (Reusch and Feldman, 1991).

PLASMA ENDOGENOUS ACTH CONCENTRATION

Stringent and meticulous sample handling is crucial since ACTH activity in the plasma will reduce rapidly resulting in falsely low values and incorrect interpretation. The endogenous ACTH assay used must be validated for use in dogs.

Measurement of basal endogenous ACTH concentrations is of no value in the diagnosis of hyperadrenocorticism because of the episodic secretion of ACTH in healthy dogs and the overlapping values with those dogs with hyperadrenocorticism.

Endogenous ACTH concentrations in healthy dogs range from 13 to 46 pg/ml. Dogs with adrenal tumours have very low endogenous ACTH concentrations (< 5 pg/ml) whereas cases with pituitary-dependant hyperadrenocorticism tend to have high-normal to high concentrations (> 28 pg/ml). ACTH measurement has been shown to be an accurate method of identifying the cause of hyperadrenocorticism (Gould et al., 2001). It has also been recognised that there is a positive correlation between the plasma ACTH concentration and the size of the pituitary mass in pituitary-dependent hyperadrenocorticism (Théon and Feldman, 1998).

DIAGNOSTIC IMAGING

Advances in diagnostic imaging have improved the ability of clinicians to identify the cause of spontaneous hyperadrenocorticism and the extent of the underlying pathology so that treatment can be directed more specifically to the individual patient. However, finding a pituitary or adrenal mass does not necessarily mean the presence of a functional tumour. Therefore, diagnostic imaging should always be interpreted in association with the clinical signs and endocrine test results.

RADIOGRAPHY

Radiographic examination of the thorax and abdomen is advisable in all cases of suspected or proven hyperadrenocorticism. Although positive diagnostic information is only obtained in the small number of cases in which adrenal enlargement or mineralisation can be detected, survey radiographs may reveal significant intercurrent disease, which might alter the prognosis.

Normal adrenal glands are not visible on abdominal radiographs and adrenomegaly is a very uncommon finding on abdominal radiographs. If adrenomegaly is seen then it suggests gross enlargement, which is typical, though not diagnostic, of an adrenal tumour. Unilateral mineralisation in the region of an adrenal gland also suggests the possibility of an adrenal tumour, although the presence of mineralisation cannot be used to distinguish benign from malignant tumours.

ABDOMINAL ULTRASONOGRAPHY

The normal adrenal gland is somewhat flattened, bi-lobed and hypoechoic compared with the surrounding tissues. The medulla of the normal adrenal is slightly hyperechoic compared to the cortex. The maximum dimensions (length x thickness) of normal canine adrenal glands are in the range 10-52 mm x 2-12 mm (Grooters et al., 1995, Douglass et al., 1997). There is poor correlation between these dimensions and body weight and there are no published normal adrenal measurements for different breeds of dog.

The challenge for the ultrasonographer is to consistently distinguish between normal, hyperplastic and neoplastic glands. Although the adrenal glands of dogs with pituitary- dependent hyperadrenocorticism have been characterised as being symmetrically enlarged and of normal conformation, the diagnosis of adrenal hyperplasia is a somewhat subjective evaluation.

Although a thickness of greater than 7.5 mm for the left adrenal gland is considered to provide the best sensitivity and specificity as a diagnostic test for pituitary-dependent hyperadrenocorticism (Bartez et al., 1995), increases in adrenal thickness are not specific enough to warrant the use of adrenal ultrasonography as a screening test for hyperadrenocorticism since there is considerable overlap between normal and hyperplastic adrenal gland measurements (Gould et al. 2001).

Abdominal ultrasonography can also detect adrenocortical tumours (Kantrowitz et al., 1986). The presence of bilateral adrenal tumours has been reported, but is rare (Ford et al, 1993). There is a propensity for malignant adrenal tumours to invade nearby vessels and surrounding tissues, therefore a thorough ultrasonographic examination of adjacent vessels and tissues should be performed.

Mineralisation is frequently associated with both benign and malignant adrenocortical tumours in the dog and acoustic shadowing may aid in localising the adrenal tumour. Ultrasonography, however, cannot differentiate a functional adrenocortical tumour from a non-functional tumour, a phaeochromocytoma, a metastatic lesion or a granuloma.

If an adrenal mass is identified, the liver, spleen and kidneys should also be examined ultrasonographically for evidence of metastases.

COMPUTED TOMOGRAPHY AND MAGNETIC RESONANCE IMAGING

Computed tomography (CT) and magnetic resonance imaging (MRI) have proved useful in the diagnosis of adrenal tumours, adrenal hyperplasia and large pituitary tumours but both techniques are expensive and not always widely available (Voorhout et al., 1988; Bertoy et al., 1995; Duesberg et al., 1995). CT can also identify invasion of the caudal vena cava by the tumour and adhesions between the adrenal gland and the caudal vena cava.

Although no comparative studies have been carried out in dogs, magnetic resonance imaging has been found to be superior to CT in detecting ACTH-secreting tumours of the pituitary gland in human beings. MRI is extremely sensitive and can detect pituitary tumours as small as 3 mm at their greatest height (Bertoy et al., 1995). About 50 per cent of dogs with pituitary-dependent hyperadrenocorticism have a detectable pituitary mass on MRI. This mass usually continues to grow despite treatment with mitotane or trilostane (Bertoy et al., 1996).

Correlation between pituitary tumour size and the presence, or development, of neurological signs is not clear cut. Large pituitary tumours (up to 12 mm in diameter) have been shown to be present without causing neurological signs, whereas pituitary masses ranging in size from 8 to 24 mm may be associated with neurological signs (Duesberg et al., 1995). In those cases with neurological signs, MRI or CT examination of the brain is essential for accurately planning therapy if pituitary irradiation is to be considered.

TREATMENT OF PITUITARY - DEPENDENT HYPERADRENOCORTICISM

TRILOSTANE

Trilostane is a synthetic steroid with no inherent hormonal activity. It acts as a competitive, and therefore reversible, inhibitor of the 3ß-hydroxysteroid dehydrogenase enzyme system which blocks adrenal synthesis of glucocorticoids, mineralocorticoids and sex hormones. The clinical use of trilostane in canine HAC, and in particular PDH, has now been evaluated in several published clinical studies from centres across the world. Trilostane is safer than mitotane for humans to handle.

STARTING DOSE

The currently recommended starting dose is in the range 2 to 5 mg/kg per day. A range of capsule sizes is available in the UK but in other countries reformulation may be necessary for small dogs. There are no studies, which directly compare different frequencies of trilostane administration. However it has been demonstrated that the effect of trilostane on basal and ACTH stimulated cortisol is considerably less than 24 hours in most cases. When some poorly controlled dogs are switched to twice daily dosing, their clinical condition improves. However the overall results obtained by twice daily dosing are not superior to those obtained by once daily and therefore it is probably not necessary to divide the starting

dose for all dogs. In one study in which trilostane was used twice daily in all dogs there was a higher rate of adverse incidents when compared to other studies.

MONITORING

Most clinical studies to date have used the clinical signs and the ACTH stimulation test as the primary methods of assessing control. In these studies trilostane caused significant reductions in both the mean basal and post-ACTH stimulation cortisol concentrations in dogs with HAC in the first month of treatment. Furthermore these improvements were also maintained in the study populations for the duration of the trial. However, despite its widespread use, the ACTH stimulation test has never been validated for trilostane therapy.

Various different timings and cortisol target levels for the ACTH stimulation test when used to monitor trilostane therapy have been used. The lower the target range the greater the chance of hypoadrenocorticism. As the effects of trilostane are relatively short lived, the results obtained by an ACTH stimulation test varies considerably with the time of testing relative to dosing .

The author currently recommends a target range for the post ACTH cortisol concentration is 40 to 120 nmol/l for ACTH stimulation tests started 2 to 4 hours after dosing; however if dogs have a post-ACTH cortisol concentration of 120–200 and are responding well to treatment then an increase in monitoring rather than dose may be more acceptable to the owners. Other methods of monitoring trilostane are still under active investigation.

The short duration of action of trilostane has a protective effect against the development of hypoadrenocorticism. Many dogs with no serum cortisol response to ACTH stimulation 2 – 3 hours post trilostane dosing, do not develop signs of hypoadrenocorticism. In contrast some dogs that have a target level post ACTH stimulation test serum cortisol will still exhibit signs of HAC.

EFFICACY AND SURVIVAL

Trilostane has been found to be over 67%-90% effective in resolving the various signs of HAC over 3 to 6 months.

The reported median survival times of dogs treated with trilostane range from 662 to 900 days and is comparable or better than the median survival times of dogs treated with mitotane (which ranged from 708 to 720 days in the same studies) . However one study used twice daily trilostane and a non-selective adrenocorticolytic protocol. In those countries which do not currently regard either routine twice daily dosing with trilostane or non-selective adrenocorticolysis with mitotane as first choice protocols this study has more relevance to animals that have failed a conventional first choice protocol.

SIDE EFFECTS

The prevalence of side effects with trilostane is generally considered to be lower than with mitotane. If the various clinical studies are combined, then only 16% of dogs treated with trilostane developed adverse effects that may have been attributable to the drug. This figure compares favourably to those reported with mitotane (25 to 42%).

If failure to respond is regarded as an adverse effect then it is probably the most common adverse effect of trilostane administration. In these cases an increase in the dose (and /or frequency) or a change to an alternative medication (such as mitotane) is indicated.

Another common side effect is an increase in the size of the adrenal glands and a change in the echotexture (Mantis and others 2003)

ADRENAL NECROSIS.

The most serious side effect of trilostane that has been identified to date is acute adrenal necrosis. Although deaths are rare, subclinical histopathological evidence of adrenal necrosis is more common. Necrosis of the adrenal cortex cannot be directly explained by the competitive inhibition of steriodogenesis. The development of adrenal necrosis could be due to the hypersecretion of ACTH which, as well as increasing the size of the adrenals, may also, paradoxically, result in necrosis and haemorrhage of the adrenal glands.

HYPOADRENOCORTICISM.

Overdosing with trilostane will result in hypoadrenocorticism. Most cases of hypoadrenocorticism associated with trilostane recover rapidly following temporary cessation of the drug but continue to require the drug to control the clinical signs. Most affected cases have typical electrolyte changes (hyponatremia, hyperkalemia) typical of hypoadrenocorticism.

HYPERKALAEMIA.

Some clinical studies of trilostane have recorded a mild increase in median serum potassium concentrations. Dogs that develop hyperkalemia but whose cortisol levels are adeqaute do not appear to have a low aldosterone concentration (Ramsey and Neiger, unpublished observations). The mechanism of action of this hyperkalemia has not been identified. Any trilostane treated dog with a mild increase in potassium should be checked with an ACTH stimulation test, rather than empirically reducing the dose. Trilostane can then be safely withheld whilst waiting for the results of the test.

OTHER SIDE EFFECTS

Trilostane is associated with vomiting and diarrhoea in some dogs independently of any effects on cortisol levels. The best treatment is to administer the tablets with food or to change to an alternative medication.

Successful treatment with trilostane might also lead to the development of previously suppressed immune-mediated, inflammatory or neoplastic diseases however, so far, there have been no reports of these side effects. There is also a theoretical risk that trilostane- induced adrenal hyperplasia could develop into adrenal tumours or that it could cause an increase in the size of pituitary tumours. However, again no evidence for this has been published.

MITOTANE THERAPY

Mitotane (op'-DDD, Lysodren, Bristol Laboratories) is an adrenocorticolytic drug. It selectively destroys the zona fasciculata and zona reticularis while tending to preserve the zona glomerulosa. Mitotane requires a Special Treatment Authorisation from the Veterinary Medicines Directorate for its use in the UK. It should therefore only be used in the treatment of pituitary-dependent hyperadrenocorticism when trilostane has been shown to be ineffective, when adverse effects have meant that trilostane cannot be used, or when pre- existing disorders preclude the use of trilostane.

PRE-TREATMENT ASSESSMENT

Mitotane therapy should only be considered once the diagnosis of hyperadrenocorticism has been confirmed. Because of its powerful effects, it should never be used empirically. Before treatment is instigated, the dog's daily water consumption should be measured over at least two consecutive 24-hour periods. If the water intake and appetite are not increased then a baseline lymphocyte count and pre-treatment cortisol concentrations, both before and after ACTH stimulation, are required in order that the effects of treatment can be monitored.

INITIAL TREATMENT

The author prefers to have his patients hospitalised for the initial course of treatment, although many clinicians have dogs treated by their owners at home, with the owners doing the necessary monitoring.

Mitotane is given orally at a dose rate of 50 mg/kg/day. It should be administered with food, since it is a fat soluble drug and its absorption is poor when administered orally to fasted animals. Daily mitotane therapy should be continued until any of the following changes are noted:

• The water intake of a polydipsic dog drops to below 60 ml/kg/day

• The dog takes longer to consume its meal than before treatment or stops eating completely

• The dog develops vomiting or has diarrhoea

• The dog becomes listless and depressed.

The initial mitotane course is then stopped and the dog put on maintenance therapy (see below). The importance of close monitoring of the patient during this period cannot be over-emphasised.

Mitotane therapy is comparatively safe and adverse effects, which occur most frequently, for example, anorexia, vomiting or diarrhoea, are rarely serious providing they are noticed early so that mitotane therapy can be withheld.

The majority of dogs with pituitary-dependent hyperadrenocorticism require between 7 and 14 days treatment with an average of 10 days before water consumption reduces to below 60 ml/kg/day.

MAINTENANCE THERAPY

Having produced sufficient adrenocortical damage with daily mitotane treatment, it is important to continue therapy, albeit at a lower dose, otherwise the adrenal cortex will regenerate.

Mitotane is given at a dose of 50 mg/kg/week with food. Cases that are well controlled may sleep for a few hours after the weekly dose and for that reason it is often recommended that the treatment is given in the evening. More profound depression or weakness requires re-evaluation using the ACTH stimulation test and possibly a reduction or splitting of the maintenance dose. Failure to control the polydipsia may require an increased dose of mitotane.

RE-EXAMINATION

Treated dogs should be re-examined 6 to 8 weeks after completion of the initial therapy, unless there are any problems. Marked improvement should be noted at this time.

Re-evaluation every 3 to 6 months is recommended for the remainder of the animal's life. The dosage of mitotane should be adjusted according to the results of ACTH stimulation testing. The goal of therapy is to achieve an ACTH test result with serum cortisol concentrations between 20 and 120 nmol/l. Relapses and episodes of overdosage do occur. Relapses (serum cortisol >200 nmol/l) may require a short course of daily mitotane therapy or an increase in the maintenance dosage. Overdosage (serum cortisol <20 nmol/l) requires a reduction in the frequency or dose of maintenance therapy.

SIDE EFFECTS

Primary hypoadrenocorticism (Addison’s Disease) with both glucocorticoid and mineralocorticoid insufficiency occurs in 5 to 17 per cent of treated dogs during maintenance therapy. Although Addison's disease can develop at any time during treatment, most cases of primary hypoadrenocorticism occur during the first year of treatment. There is, unfortunately, no way to predict which dogs will develop complete adrenocortical insufficiency, but if hypoadrenocorticism does develop, maintenance

mitotane therapy should be stopped and the dog treated with mineralocorticoid and glucocorticoid supplementation as for primary hypoadrenocorticism. Successful treatment with mitotane might also lead to the development of previously suppressed immune mediated, inflammatory or neoplastic diseases.

SURVIVAL DATA

The mean survival time of treated dogs was 30 months in one study, with a range of a few days to over 7 years (Dunn et al., 1995). The highest mortality was seen in the first 16 weeks of treatment and dogs which survived this period had a longer mean survival time. Other studies have shown similar survival times (Kintzer and Peterson, 1991).

OTHER TREATMENTS

PITUITARY IRRADIATION

Pituitary irradiation is indicated for dogs with neurological signs associated with pituitary tumours. CT or MR imaging of the brain is required to plan the treatment protocol. Radiotherapy using megavoltage irradiation from a linear accelerator or cobalt 60 source is required to penetrate to the depth of the pituitary gland without seriously injuring overlying soft tissues. Most treatment protocols involve the administration of 40 to 50 Gy in 3 to 4 Gy fractions (Goosens et al., 1998, Théon and Feldman, 1998). There is often a dramatic response although in some cases improvement takes several weeks.

The resolution of neurological signs parallels the reduction in size of the tumour, which can continue to decrease for a year or more after the completion of the radiotherapy. Reduction in ACTH secretion by the tumour is less predictable and if it does occur, it may not be evident for 6 to 12 months after therapy. Therefore, medical management of hyperadrenocorticism with trilostane or mitotane is indicated at least initially.

HYPOPHYSECTOMY

Hypophysectomy has been successfully performed in the dog for the treatment of pituitary- dependent hyperadrenocorticism using the trans-sphenoidal approach (Meij et al., 1998). The operation is technically difficult and should only be carried out by a surgeon with considerable skill and experience of the technique otherwise it is associated with high morbidity and mortality. In experienced hands the peri-operative mortality is 8% and the surgical failure rate (i.e. the condition recurs) is 6% (Hanson and others 2005).

A. TREATMENT OF ADRENAL-DEPENDENT HYPERADRENOCORTICISM

SURGICAL ADRENALECTOMY

Dogs with adrenal-dependent hyperadrenocorticism carry the best prognosis if the tumour can be completely removed surgically. However, animals with untreated AD-HAC represent difficult surgical candidates because of the increased anaesthetic risk (due to poor respiratory and hepatic function), hypercoagulability (leading to an increased risk of pulmonary thromboembolism and the poor vascular tone (leading to poor haemostasis). The anatomical location and surrounding blood vessels makes surgical exposure and removal difficult. Furthermore, many adrenal tumours are quite friable and haemorrhagic.

Primary wound healing is delayed, but wound breakdown is very rare. Unilateral adrenalectomy therefore requires considerable experience and expertise. Acute post- operative hypoadrenocorticism due to pre-existing contralateral adrenal atrophy is common. Post-operative intensive care facilities are, therefore, essential.

Inexperienced surgeons or those without adequate facilities, including assistance in anaesthesia, should not attempt adrenalectomy. Even in referral institutes, peri-operative mortality rates are often in the range of 20 to 30 per cent (van Sluijs and others, 1995, Schwartz and others 2008). Almost all animals that undergo adrenalectomy suffer some sort of complication.

If surgery is an option then pre-operative staging of the adrenal tumour should include thoracic radiographs and abdominal ultrasound or CT to assess the presence of vascular invasion and metastatic spread. Administration of trilostane or mitotane is recommended by some authors in order to attempt to control the hyperadrenocorticism before surgery. Pre-operative stabilization probably improves survival, but this has not been clearly demonstrated. Mitotane may be less useful than trilostane or ketoconazole in this respect, because it may make the tumour more friable but objective data is not available..

During and following surgery, glucocorticoid and mineralocorticoid supplementation are required. For this purpose intravenous hydrocortisone would is a logical choice but a combination of fludrocortisone and prednisolone by mouth can be used as well. Therapy should be slowly discontinued over a period of weeks to months depending on the results of electrolyte monitoring and assessment of appetite.

If surgery is successful and the patient survives the perioperative period then the prognosis is good. In one study, the median survival time was just less than 2 years, though some dogs survived for longer than 4 years (van Sluijs et al., 1995).

MITOTANE THERAPY

Mitotane, o.p.' -DDD (Lysodren, Bristol Laboratories) is effective and relatively safe in dogs with adrenal-dependent hyperadrenocorticism. Dogs with adrenal tumours however, tend to be more resistant to mitotane than dogs with pituitary-dependent hyperadrenocorticism (Feldman et al., 1992). Generally dogs with adrenal-dependent hyperadrenocorticism require higher daily induction doses (50-75 mg/kg/day) and a longer period of induction (>14 days) than dogs with pituitary-dependent hyperadrenocorticism

(Kintzer and Peterson, 1994). However in this study about 20 per cent of cases responded successfully to the recommended protocol for pituitary-dependent hyperadrenocorticism. Frequent monitoring of treatment by ACTH stimulation testing is important to ensure adequate control of the hyperadrenocorticism.

Maintenance doses are also generally higher (75-100 mg/kg/week) and again frequent monitoring of the cortisol response to ACTH stimulation is required to maintain optimal control of the disease. Adverse effects of treatment are similar to those described for pituitary-dependent hyperadrenocorticism. Those dogs requiring higher dose rates tend to be more prone to adverse effects. The adrenal tumour and metastatic mass will often reduce in size due the cytotoxic effects of mitotane, but in other cases the tumour will continue to grow despite increasing doses of mitotane. In one study of adrenocortical tumours treated using mitotane therapy, the median survival time was 11 months with a range of a few weeks to more than 5 years (Kintzer and Peterson, 1994).

TRILOSTANE THERAPY

Trilostane has also been used to control the clinical signs in adrenal-dependent hyperadrenocorticism with some success (Benchekroun and others 2008). Starting doses are the same as for pituitary dependent hyperadrenocorticism however higher doses may become necessary as the tumour progresses. In one case with an adrenal tumour an 80- week survival was reported on trilostane using a dose of up to 17.2 mg/kg once daily (Eastwood et al., 2003). Until larger scale studies are published, recommendations on the frequency of dosing and likely prognosis are not possible. As an enzyme inhibitor, trilostane provides only control of the clinical signs without treating the underlying neoplastic disease process.

REFERENCES

Alenza DP, Arenas C, Lopez ML, MELIAN C. (2006) Long-term efficacy of trilostane administered twice daily in dogs with pituitary-dependent hyperadrenocorticism. Journal of the American Animal Hospital Association 42, 269-76.

Anderson CR. Birchard SJ. Powers BE. Belandria GA. Kuntz CA. Withrow SJ. (2001) Surgical treatment of adrenocortical tumors: 21 cases (1990-1996) Journal of the American Animal Hospital Association 37, 93-7

Bartez, P.Y. Nyland, T.G. & Feldman, E.C. (1995) Ultrasonographic evaluation of the adrenal glands in dogs. Journal of the American Veterinary Medical Association 207, 1180- 1183.

Barker E., Campbell S., Tebb A., Neiger R., Herrtage M., & Ramsey I. (2005) A comparison of the survival times of dogs treated for hyperadrenocorticism with trilostane or mitotane Journal of Veterinary Internal Medicine 19 : 810-815

Bell R. Neiger R., McGrotty Y. & Ramsey IK. (2006) Effects of once daily trilostane administration on cortisol concentrations and ACTH responsiveness in hyperadrenocorticoid dogs Veterinary Record 159 : 277-281

Benchekroun G, de Fornel-Thibaud P, Lafarge S, et al. (2008) Trilostane therapy for hyperadrenocorticism in three dogs with adrenocortical metastasis. Veterinary Record 163, 190-2.

Bertoy, E.H., Feldman, E.C., Nelson, R.W., Duesberg, C.A., Kass, P.H., Reid, M.H. & Dublin, A.B. (1995) Magnetic resonance imaging of the brain in dogs with recently diagnosed but untreated pituitary-dependent hyperadrenocorticism. Journal of the American Veterinary Medical Association 206, 651-656.

Bertoy, E.H., Feldman, E.C., Nelson, R.W., Dublin, A.B., Reid, M.H. & Feldman, M.S. (1996) One-year follow-up evaluation of magnetic resonance imaging of the brain of dogs with pituitary-dependent hyperadrenocorticism. Journal of the American Veterinary Medical Association 208, 1268-1273.

Braddock JA, Church DB, Robertson ID, and Watson AD. (2003) Trilostane treatment in dogs with pituitary-dependent hyperadrenocorticism. Australian Veterinary Journal. 81, 600- 7

Castillo VA, Gómez NV, Lalia JC, Cabrera Blatter MF, García JD (2008) Cushing's disease in dogs: cabergoline treatment. Research in Veterinary Science. 85, 26-34.

Chapman, P.S., Mooney, C.T., Ede, J., Evans, H., O’Connor, J., Pfeiffer, D.U. & Neiger, R. (2003) Evaluation of the basal and post-adrenocorticotrophic hormone serum concentrations of 17-hydroxyprogesterone for the diagnosis of hyperadrenocorticism in dogs. Veterinary Record 153, 771-775.

Chapman, P.S., Kelly, D.F., Archer, J., Brockman, D.J. & Neiger, R. (2004) Adrenal necrosis in two dogs receiving trilostane for the treatment of hyperadrenocorticism. Journal of Small Animal Practice 45, 307-10.

Clemente M, De Andrés PJ, Arenas C, MELIÁN C, MORALES M, PÉREZ -ALENZA MD (2007) Comparison of non-selective adrenocorticolysis with mitotane or trilostane for the treatment of dogs with pituitary-dependent hyperadrenocorticism. Veterinary Record. 161, 805-9.

Douglass, J.P., Berry, C.R. & James, S. (1997) Ultrasonographic adrenal gland measurements in dogs without evidence of adrenal disease. Veterinary Radiology and Ultrasound 38, 124-130.

Duesberg, C.A., Feldman, E.C., Nelson, R.W., Bertoy, E.H., Dublin, A.B. & Reid, M.H. (1995) Brain magnetic resonance imaging for the diagnosis of pituitary macrotumours. Journal of the American Veterinary Medical Association 206, 675-662.

Dunn, K.J, Herrtage, M.E. & Dunn, J.K. (1995) Use of ACTH stimulation tests to monitor the treatment of canine hyperadrenocorticism. Veterinary Record 137, 161-165.

Eastwood, J.M., Elwood, C.M. & Hurley, K.J. (2003) Trilostane treatment of a dog with functional adrenocortical neoplasia. Journal of Small Animal Practice 44, 126-131.

Feldman, E.C., Nelson, R.W., Feldman, M.S. & Farver, T.B. (1992) Comparison of mitotane treatment for adrenal tumor versus pituitary-dependent hyperadrenocorticism in dogs. Journal of the American Veterinary Medical Association 200, 1642-1647.

Ferguson, D.C. & Peterson, M.E. (1992) Serum free and total iodothyronine concentrations in dogs with hyperadrenocorticism. American Journal of Veterinary Research 53,1636-1640.

Ford, S.L., Feldman, E.C. & Nelson, R.W. (1993) Hyperadrenocorticism caused by bilateral adrenocortical neoplasia in dogs: four cases (1983-1988). Journal of the American Veterinary Medical Association 202, 789-792.

Galac, S., Kooistra, H.S., Teske, E. & Rijnberk, A. (1997) Urinary corticoid/creatinine ratios in the differentiation between pituitary-dependent hyperadrenocorticism and hyperadrenocorticism due to adrenocortical tumour in the dog. Veterinary Quarterly 19, 17-20.

Galac, S., Kooistra, H.S., Kirpensteijn, J., van den Ingh, T.S.G.A.M., Voorout, G., Mol, J.A. & Meij, B.P. (2003) Hyperadrenocorticism in a dog due to ectopic ACTH secretion. Journal of Veterinary Internal Medicine 17, 737.

Galac S, Buijtels JJ, Mol JA, et al. (2008) Effects of trilostane on the pituitary-adrenocortical and renin-aldosterone axis in dogs with pituitary-dependent hypercortisolism. Veterinary Journal. 2008 [Epub ahead of print].

Galac S, Buijtels JJ, Kooistra HS. (2009) Urinary Corticoid : Creatinine Ratios in Dogs with Pituitary-Dependent Hypercortisolism during Trilostane Treatment Journal of Veterinary Internal Medicine (Epub ahead of print)

Goossens, M.M.C., Feldman, E.C., Theon, A.P. & Koblik, P.D. (1998) Efficacy of cobalt 60 radiotherapy in dogs with pituitary-dependent hyperadrenocorticism. Journal of American Veterinary Medical Association 212, 374-376.

Gould, S.M., Baines, E.A., Mannion, P.A., Evans, H. & Herrtage, M.E. (2001) Use of endogenous ACTH concentration and adrenal ultrasonography to distinguish the cause of canine hyperadrenocorticism. Journal of Small Animal Practice 42, 113-121.

Goy-Thollot, I., Péchereau, D., Kéroack, S., Dezempte, J-C. & Bonnet, J-M. (2002) Investigation of the role of aldosterone in hypertension associated with spontaneous pituitary-dependent hyperadrenocorticism in dogs. Journal of Small Animal Practice 43, 489492.

Greco, D.S., Peterson, M.E., Davidson, A.P., Feldman, E.C. & Komurek, K (1999) Concurrent pituitary and adrenal tumors in dogs with hyperadrenocorticism: 17 cases (1978-1995). Journal of the American Veterinary Medical Association 214, 1349-1353.

Grooters, A.M., Biller, D.S. Merryman, J. (1995) Ultrasonographic parameters of normal canine adrenal glands: comparison to necropsy findings. Veterinary Radiology and Ultrasound 36, 126-130.

Grooters, A.M., Biller, D.S., Theisen, S.K. & Miyabayashi, T. (1996) Ultrasonographic characteristics of adrenal glands in dogs with pituitary-dependent hyperadrenocorticism: comparison with normal dogs. Journal of Veterinary Internal Medicine 10, 110-115.

Guptill, L., Scott-Moncrieff, J.C., Bottoms, G., Glickman, L., Johnson, M., Glickman, N., Nelson, R., & Bertoy, E. (1997) Use of urine cortisol: creatinine ratio to monitor treatment response in dogs with pituitary-dependent hyperadrenocorticism. Journal of the American Veterinary Medical Association 210, 1158-1161.

Hanson JM, van 't HM, Voorhout G, Teske E, Kooistra HS, Meij BP. (2005) Efficacy of transsphenoidal hypophysectomy in treatment of dogs with pituitary-dependent hyperadrenocorticism. Journal of Veterinary Internal Medicine 19, 687-94.

Hurley, K.J. & Vaden, S.L. (1998) Evaluation of urine protein content in dogs with pituitary-dependent hyperadrenocorticism. Journal of the American Veterinary Medical Association 212, 369-373.

Kantrowitz, C.M., Nyland, T.G. & Feldman, E.C. (1986) Adrenal ultrasonography in the dog: detection of tumours and hyperplasia in hyperadrenocorticism. Veterinary Radiology 27, 91-96.

Kaplan, A.J., Peterson, M.E. and Kemppainen, R.J. (1995) Effects of disease on the results of diagnostic tests for use in detecting hyperadrenocorticism in dogs. Journal of the American Veterinary Medical Association 207, 445-451.

Kemppainen, R.J. & Sartin, J.L. (1984) Evidence for episodic but not circadian activity in plasma concentrations of adrenocorticotropin, cortisol and thyroxine in dogs. Journal of Endocrinology 103, 219-226.

Kintzer, P.P. & Peterson, M.E. (1991) Mitotane (o,p'-DDD) treatment of 200 dogs with pituitary-dependent hyperadrenocorticism. Journal of Veterinary Internal Medicine 5, 182- 190.

Kintzer, P.P. & Peterson, M.E. (1994) Mitotane treatment of 32 dogs with cortisol- secreting adrenocortical neoplasms. Journal of the American Veterinary Medical Association 205, 54-60.

Lien YH, and Huang HP (2008) Use of ketoconazole to treat dogs with pituitary-dependent hyperadrenocorticism: 48 cases (1994-2007). Journal of the American Veterinary Medical Association 233, 1896-901.

Long S., Michieletto, A. Anderson TJ., Williams A. Knottenbelt CM (2003) Suspected pituitary apoplexy in a German short-haired pointer Journal of Small Animal Practice 44 : 497-502

Meij, B.P., Voorhout, G., van den Ingh, T.S.G.A.M., Hazewinkel, H.A.W., Teske, E. & Rijnberk, A. (1998) Results of transspenoidal hypophysectomy in 52 dogs with pituitary- dependent hyperadrenocorticism. Veterinary Surgery 27, 246-261.

Mantis P. Lamb CR. Witt AL. Neiger R. (2003) Changes in ultrasonographic appearance of adrenal glands in dogs with pituitary-dependent hyperadrenocorticism treated with trilostane. Veterinary Radiology & Ultrasound 44, 682-5

Montgomery, T.M., Nelson, R.W., Feldman, E.C., Robertson, K. & Polonsky, K.S. (1996) Basal and glucagon-stimulated plasma C-peptide concentrations in healthy dogs, dogs with diabetes mellitus, and dogs with hyperadrenocorticism. Journal of Veterinary Internal Medicine 10, 116-122.

Mueller, C., Sieber-Ruckstuhl, N., Wenger, M., Kaser-Hotz, B., and Reusch, C.E. (2006) Low-dose dexamethasone test with ‘inverse’ results a possible new pattern of cortisol response Veterinary Record 159, 489-491

Neiger, R., Ramsey, I., O’Connor, J., Hurley, K.J. & Mooney, C.T. (2002) Trilostane treatment of 78 dogs with pituitary-dependent hyperadrenocorticism. Veterinary Record 150, 799-804.

Norman, E.J., Thompson, H. & Mooney, C.T. (1999) Dynamic adrenal function testing in eight dogs with hyperadrenocorticism associated with adrenocortical neoplasia. Veterinary Record 144, 551-554.

Pérez AM, Guerrero B, Melián C, Ynaraja E, Peña L. (2002) Use of aminoglutethimide in the treatment of pituitary-dependent hyperadrenocorticism in the dog. Journal of Small Animal Practice 43, 104-8.

Peterson, M.E., Krieger, D.T., Drucker, W.D., & Halmi, N.S. (1982a) Immunocytochemical study of the hypophysis in 25 dogs with pituitary-dependent hyperadrenocorticism. Acta Endocrinologica 101, 15-24.

Peterson, M.E., Ferguson, D.C., Kintzer, P.P., and Drucker, W.D. (1984) Effects of spontaneous hyperadrenocorticism on serum thyroid hormone concentrations in the dog. American Journal of Veterinary Research 45, 2034-2038.

Ramsey, IK & Herrtage, M.E. (1998) The effect of thyrotropin releasing hormone on thyrotropin concentrations in euthyroid, hypothyroid and hyperadrenocorticoid dogs. Journal of Veterinary Internal Medicine 12, 235.

Ramsey, IK, Tebb, A., Harris, E., Evans, H., and Herrtage, M.E. (2005) Hyperparathyroidism in dogs with hyperadrenocorticism Journal of Small Animal Practice 46, 531-536

Ramsey IK, Richardson J, Lenard Z, et al. (2008) Persistent isolated hypocortisolism following brief treatment with trilostane. Australian Veterinary Journal 86, 491-5.

Reusch, C.E. and Feldman, E.C. (1991) Canine hyperadrenocorticism due to adrenocortical neoplasia: pretreatment evaluation in 41 dogs. Journal of Veterinary Internal Medicine 13, 291-301.

Reusch, C.E., Steffen, T. & Hoerauf, A. (1999) The efficacy of L-deprenyl in dogs with pituitary-dependent hyperadrenocorticism. Journal of Veterinary Internal Medicine 5, 3-10.

Reusch CE, Sieber-Ruckstuhl N, Wenger M, et al. (2007) Histological evaluation of the adrenal glands of seven dogs with hyperadrenocorticism treated with trilostane. Veterinary Record 160, 219-24.

Rijnberk, A., Van Wees, A., & Mol, J.A. (1988) Assessment of two tests for the diagnosis of canine hyperadrenocorticism. Veterinary Record 122, 178-180.

Ristic, J.M.E., Ramsey, I.K., Heath, F.M., Evans, H.J. & Herrtage, M.E. (2002) The use of 17-hydroxyprogesterone in the diagnosis of canine hyperadrenocorticism. Journal of Veterinary Internal Medicine 16, 433-439.

Ruckstuhl, N.S., Nett, C.S. & Reusch, C.E. (2002) Results of clinical examinations, laboratory tests, and ultrasonography in dogs with pituitary-dependent hyperadrenocorticism treated with trilostane. American Journal of Veterinary Research 63, 506-512.

Scavelli TD, Peterson ME, Matthiesen DT. (1986) Results of surgical treatment for hyperadrenocorticism caused by adrenocortical neoplasia in the dog: 25 cases (1980-1984). Journal of the American Veterinary Medical Association 189, 1360-4

Schwarz, T., Störk, C.K., Mellor, D.& Sullivan, M. (2000) Osteopenia and other radiographic signs in canine hyperadrenocorticism. Journal of Small Animal Practice 41, 491-495.

Schwartz P, Kovak JR, Koprowski A, Ludwig LL, Monette S, Bergman PJ. (2008) Evaluation of prognostic factors in the surgical treatment of adrenal gland tumors in dogs: 41 cases (1999-2005). Journal of the American Veterinary Medical Association 232, 77-84.

Smiley, L.E. and Peterson, M.E. (1993) Evaluation of a urine cortisol:creatinine ratio as a screening test for hyperadrenocorticism in dogs. Journal of Veterinary Internal Medicine 7 163-168.

Syme, H.M., Scott-Moncrieff, J., Treadwell, N.G., Thompson, M.F., Snyder, P.W., White, M.R. & Oliver, J.W. (2001) Hyperadrenocorticism associated with excessive sex hormone production by an adrenocortical tumor in two dogs. Journal of the American Veterinary Medical Association 219, 1725-1728.

Teske, E., Rothuizen, J., de Bruijne, J.J. & Rijnberk, A. (1989) Corticosteroid-induced alkaline phosphatase isoenzyme in the diagnosis of canine hypercorticism. Veterinary Record 125, 12-14.

Théon, A.P. & Feldman, E.C. (1998) Megavoltage irradiation of pituitary macrotumours in dogs with neurological signs. Journal of American Veterinary Medical Association 213, 225- 231. van Sluijs, F.J., Sjollema, B.E., Voorhout, G., van den Ingh, T.S.G.A.M. & Rijnberk, A. (1995) Results of adrenalectomy in 36 dogs with hyperadrenocorticism caused by adrenocortical tumour. Veterinary Quarterly 17, 113-116.

Vaughan MA, Feldman EC, Hoar BR, et al. (2008) Evaluation of twice-daily, low-dose trilostane treatment administered orally in dogs with naturally occurring hyperadrenocorticism. Journal of the American Veterinary Medical Association 232, 1321-8.

Voorhout, G., Stolp, R., Lubberink, A.A.M.E. & Van Waes, P.F.G.M. (1988). Computed tomography in the diagnosis of canine hyperadrenocorticism not suppressible by dexamethasone. Journal of the American Veterinary Medical Association 192, 641-646.

Voorhout, G., Stolp, R., Rijnberk, A. & van Waes, P.F.G.M. (1990) Assessment of survey radiography and comparison with x-ray computed tomography for detection of hyperfunctioning adrenocortical tumors in dogs. Journal of the American Veterinary Medical Association 196, 1799-1803.

ATYPICAL HYPERADRENOCORTICISM

Michael E Herrtage M.A., B.V.Sc., D.V.Sc., D.V.R., D.V.D., D.S.A.M., M.R.C.V.S., Dip. E.C.V.I.M., Dip. E.C.V.D.I. Department of Veterinary Medicine University of Cambridge

Hyperadrenocorticism (HAC), or Cushing’s syndrome, is one of the most common endocrinopathies of older dogs. Common tests for screening dogs for HAC include the ACTH stimulation test, the low-dose dexamethasone suppression (LDDS) test, and the urine cortisol:creatinine ratio (UCCR). Atypical hyperadrenocorticism is considered when dogs have clinical signs of hypercortisolaemia, no evidence of a sex hormone-secreting adrenal tumor, and HAC screening test results within the normal reference range. Both pituitary-dependent and adrenal-dependent atypical hyperadrenocorticism cases have been reported (Norman et al., 1999, Ristic et al., 2001, Syme et al., 2001).

ADDITIONAL TESTS FOR ATYPICAL HAC

There are breed-specific variations in clinical presentations and responses to diagnostic tests. Some cases of HAC have classical clinical signs and changes on routine haematology and biochemistry but equivocal results on the specific endocrine tests described above; these are termed atypical HAC. Scottish terriers seem particularly affected by this situation. If, on repetition of the standard tests outlined above, the results remain inconclusive and the clinical signs persist, then further tests for atypical forms of HAC can be undertaken.

ACTH STIMULATION OF 17-HYDROXYPROGESTERONE

The measurement of 17-OHP before and after ACTH stimulation may be useful in helping to confirm the diagnosis of atypical HAC (Ristic et al., 2002, Benitah et al., 2005, Monroe et al., 2012). In atypical HAC there may be a derangement of the steroid production pathway and some of the precursors of cortisol, such as 17-OHP, may be abnormally increased. Both pituitary-dependent and adrenal-dependent atypical HAC cases have been reported. However this is a controversial area of endocrinology and other authors have argued against the use of this term and test (Behrend and others 2013).

The method is identical to that described above for the standard ACTH stimulation test and thus measurements of 17-OHP can be made on the same samples after cortisol concentrations have been measured. 17-OHP concentrations are stable in plasma at 4°C for several weeks.

In normal dogs, post-ACTH 17-OHP concentrations are mostly between 1.0 and 8.0 nmol/l. In dogs with classical and atypical hyperadrenocorticism plasma 17-OHP concentrations show an exaggerated response to ACTH stimulation with concentrations increasing to between 6.5 and 38 nmol/l after stimulation (Ristic et al., 2002). There is a

degree of overlap between normal and affected animals and there is some controversy over the cut off value for the diagnosis of HAC. One study suggested a post-ACTH stimulation 17-OH concentration of >8.5 nmol/l could be used as a cut off with a sensitivity and specificity of about 70%; but a few normal dogs may have post-ACTH 17-OHP concentrations as high as 17 nmol/l and dogs with ‘stressful’ diseases may be as high as 38 nmol/l (Chapman et al ., 2003). There are also gender differences in post ACTH 17-OHP values with entire females having the highest concentrations (Benitah et al, 2005).

The test is best used to identify confirmatory evidence of abnormalities of steroid metabolism in animals with considerable clinical evidence of such abnormalities. All studies emphasise that the ACTH stimulation of 17-hydroxyprogesterone is not superior to cortisol, but may be useful when the cortisol is not diagnostic. It is unlikely that the 17- hydroxyprogesterone produces clinical signs on its own but rather is serving as a marker for the abnormalities of steroid metabolism.

ACTH STIMULATION OF OTHER STEROID HORMONES

ACTH will also stimulate other adrenal steroids such as the sex hormones produced in the zonas fasciculata and reticularis. Some laboratories provide assays for these hormones including 17-hydroxyprogesterone, progesterone, oestradiol, androstenedione and testosterone. These assays are valuable for the very rare cases of sex hormone producing adrenal tumours that have been recorded in both dogs and cats (but are very common in ferrets). In such circumstances there is common agreement that the measurement of these sex hormones is useful, however the interpretation of the results depends on the tests used and practitioners are advised to seek appropriate advice from the specialist laboratory. There is little value in measuring such hormones in dogs and cats in an attempt to diagnose HAC as they are less sensitive and less specific than 17-hydroxyprogesterone alone (Hill and others 2005).

The main indication for performing these tests is in dogs with clinical signs suggestive of HAC and a confirmed adrenal mass, but negative findings on a low dose dexamethasone suppression test and an ACTH stimulation test measuring cortisol and 17 - OH progesterone (i.e. very rarely). Since HAC is a slowly progressive disease in most cases it is more appropriate to wait a few weeks and retest using a ‘standard’ ACTH stimulation test and low dose dexamethasone suppression test.

Differences in cortisol concentrations among dogs with pituitary-dependent HAC (PDH), adrenal-dependent HAC, and healthy animals have been detected when blood was collected at 30 minute intervals for 8 hours (Feldman and Nelson, 2004). Further evaluation of that data suggests equivalent results for sampling every 60 minutes versus 30 minutes. Therefore, regular sampling can reveal trends in basal cortisol concentration and recent evidence suggests that multiple sampling over an 8 hour period can differentiate normal and atypical HAC patients.

TREATMENT OF ATYPICAL HAC

Treatment of atypical HAC with trilostane or mitotane using the same protocol as for standard HAC cases has proved successful in reversing the signs of hypercortisolaemia (see lecture notes on Hyperadrenocorticism –diagnosis and treatment).

REFERENCES

Behrend EN, Kooistra HS, Nelson R, et al. (2013) Diagnosis of spontaneous canine hyperadrenocorticism: 2012 ACVIM consensus statement (small animal Journal of Veterinary Internal Medicine 27,1292-1304

Benitah N, Feldman EC, Kass PH, Nelson RW. (2005) Evaluation of serum 17- hydroxyprogesterone concentration after administration of ACTH in dogs with hyperadrenocorticism. Journal of the American Veterinary Medical Association 227,1095- 1101.

Feldman EC and Nelson RW. Canine hyperadrenocorticism (Cushing’s syndrome). In: Feldman EC, Nelson RW, eds. Canine and feline endocrinology and reproduction. 3rd ed. St Louis:Saunders Co, 2004;253-357.

Monroe WE, Panciera DL, Zimmerman KL. (2012) Concentrations of noncortisol adrenal steroids in response to ACTH in dogs with adrenal-dependent hperadrenocorticism, pituitary-dependent hyperadrenocorticism, and nonadrenal illness Journal of Veterinary Internal Medicine 26:945-952.

Norman, E.J., Thompson, H. & Mooney, C.T. (1999) Dynamic adrenal function testing in eight dogs with hyperadrenocorticism associated with adrenocortical neoplasia. Veterinary Record 144, 551-554.

THE SKIN AS A MARKER FOR INTERNAL DISEASE

Michael E Herrtage M.A., B.V.Sc., D.V.Sc., D.V.R., D.V.D., D.S.A.M., M.R.C.V.S., Dip. E.C.V.I.M., Dip. E.C.V.D.I. Department of Veterinary Medicine University of Cambridge

Cutaneous manifestations of internal disease are common and can be fairly subtle. Clinicians continue to discover these subtle clues in the skin, which alert them to investigate internal organ systems more thoroughly. In some conditions, the skin lesions may be the first clinical sign noted, but in other diseases, the cutaneous and systemic signs occur together. The skin may also just reflect the general catabolic and cachectic state brought about by the primary disease process.

FUNGAL DISEASES

In the United Kingdom, where systemic mycoses are rare, the skin changes may just reflect the cachectic state of the patient, although discharging tracts may also be seen. In cases of nasal aspergillosis or fungal rhinitis, ulceration of the rhinarium is a common manifestation and tends to differentiate the condition from other nasal diseases.

BACTERIAL DISEASES

Lyme disease is a tick-borne disease caused by the spirochaete Borrelia burgdorferi . Whilst fever and polyarthritis are prominent signs, an expanding annular lesion called erythema chronicum migrans can characterize early disease in humans. This sign has been documented in affected dogs in Europe.

Dogs with Ehrlichia spp may have crusting of the bridge of the nose or pustular or pruritic lesions due to vasculitis.

PROTOZOAL DISEASES

Leishmaniasis is a protozoal disease caused by Leishmania spp. Skin lesions occur in over 80% of dogs with visceral involvement. The most common dermatological sign is an exfoliative dermatitis, which can be generalized, but usually is most pronounced on the head, pinnae and extremities.

VIRAL DISEASES

Canine distemper can cause hyperkeratosis of the nasal planum and foot pads (hard pad disease). Young puppies may develop a widespread impetigo.

Feline herpesvirus infection can cause a pruritic and ulcerative facial dermatitis but in some cases can spread elsewhere on the body. Similar lesions have been seen with feline calicivirus.

Feline immunodeficiency virus and feline leukaemia virus infections have also been associated with a variety of cutaneous lesions.

IMMUNE-MEDIATED DISEASES

Erythema multiforme usually has an acute onset of erythematous macules and papules that spread peripherally and clear centrally. The lesions are most commonly seen at the mucocutaneous junctions, nasal mucosae, pinnae, axillae and inguinal regions. Erythema multiforme can be associated with infectious diseases, neoplasia and occasionally as a manifestation of a drug eruption.

Systemic lupus erythematosis (SLE) produces skin lesions that are highly variable. They are present together with a variety of systemic signs such as fever, polyarthritis, anaemia and glomerulonephritis. The skin changes can be non-specific cutaneous lesions or take the form of specific cutaneous lesions characterized by certain histopathological changes. The cutaneous manifestations of SLE include seborrhoeic disease, alopecia, diffuse or regional erythema, cutaneous or mucocutaneous vesicles or bullae, foot pad ulceration, hyperkeratosis, panniculitis and nasal dermatitis.

Toxic epidermal necrolysis (TEN) is an acute condition believed to be caused by a cell- mediated immunological injury. Drugs are the most common inciting cause, but neoplasia and infections have also been documented. Widespread painful erythema rapidly progresses to full-thickness necrosis of the epidermis. The most common areas affected are the oral mucosa, footpad, face and skin of the trunk.

Vasculitis is commonly believed to be immunologically mediated and may be initiated by a hypersensitivity reaction, food allergy, insect sting/bite reaction, neoplasia including mast cell tumours, SLE or idiopathic. The cutaneous lesions include poorly healing ulcers typically located in the centre of the footpads. In addition, erosions, ulcerations and crusting that affect the pinna margin or underside of the pinna. Vasculitis reactions can become systemic and may be life-threatening.

Dermatomyositis is a familial idiopathic condition affecting the skin and muscle of collies, Shetland sheepdogs and other breeds. The disease is usually seen in dogs between 6 weeks and 6 months of age. The most common sign is of myositis and asymptomatic atrophy of the muscles of mastication and of the distal limbs. Skin lesions occur in areas of mechanical trauma and are commonly seen on the face, especially around the eyes, the tips of the ears, carpal and tarsal regions and the digits and tip of the tail. Early lesions include pustules, vesicles and papules progressing to crusting and alopecia. Ulceration can be seen in severely affected dogs.

NEOPLASTIC

Sertoli cell tumour can develop in middle-aged to old male dogs. The affected testicle may be in the scrotum, inguinal canal or abdomen. The tumour may not cause gross enlargement of the testicle and can be bilateral. Up to 40% may show feminization and alopecia. In some cases skin changes occur without signs of feminization. Clinical signs are most common with crytorchid testes. Hyperoestrogenism causes hair follicles to become quiescent (telogen phase). Hair falls out leading to thinning and bilaterally symmetric alopecia affecting the genital and perineal regions. Later the flanks, ventral abdomen, chest and neck become affected. There is no pruritus and hypopigmentation around genitals may become apparent. The opposite testicle is often small, shrunken and soft. Rarely bone marrow depression (thrombocytopenia, anaemia) or torsion of affected testicle may be found.

Phaeochromocytomas are endocrine tumours arising from the adrenal medulla. The clinical signs are quite variable and often subtle. Episodic weakness and collapse, panting and dyspnoea may be seen. The dermatological manifestation is intermittent flushing, especially noticeable on the pinna.

Paraneoplastic disease consists of clinical signs that are associated with malignancies, but not directly related to tumour invasion. In the dog, these paraneoplastic syndromes include hepatocutaneous disease (necrolytic migratory erythema), nodular skin disease seen with nodular dermatofibrosis, paraneoplastic pemphigus vulgaris associated with thymic lymphoma and necrotising panniculitis associated with pancreatic carcinoma or severe pancreatitis. In the cat, these paraneoplastic dermatoses include the skin fragility syndrome seen with feline adrenal neoplasia, exfoliative dermatosis associated with feline thymoma and a bilaterally symmetrical ventral glistening associated with pancreatic carcinoma, bile duct carcinoma and thymoma.

ENDOCRINOPATHIES

Dermatological manifestations of hypothyroidism and hyperadrenocorticism have been detailed above.

Hyperthyroidism is a common endocrinopathy of middle-aged to older cats. Many of these cats have an unkempt hair coat, with excessive shedding and matting of the hair.

Diabetes mellitus may occasionally be associated with cutaneous manifestations such as pyoderma, seborrhoeic dermatitis, demodicosis, alopecia and xanthomatosis.

NUTRITIONAL DISEASE

Pansteatitis is caused by a deficiency of vitamin E. It has been reported in cats, usually fed diets containing red fish or excess cod liver oil. Affected cats are usually depressed, febrile, anorexic and painful on palpation of the skin or abdomen. Subcutaneous and abdominal fat may feel firm or nodular and draining tracts may be present from these lesions.

MISCELLANEOUS

Hepatocutaneous syndrome (necrolytic migratory erythema) is a crusting and erosive dermatitis associated with serious gastrointestinal disease, especially hepatic cirrhosis. In man, it is a distinctive cutaneous marker for a glucagon-secreting pancreatic tumour (glucagonoma). The condition affects older dogs with no apparent breed or sex predisposition. Few, if any, signs of systemic illness are seen before the skin eruption. The skin lesions are dramatic and typically painful, discrete to coalescent crusting erosions with an erythematous base. Feet and footpads, face, external genitalia, distal extremities, pressure points and pinnae are frequently involved. Blood glucose may be normal or elevated on presentation, but over 80% of cases will develop diabetes mellitus.

INTRODUCTION TO HISTOPATHOLOGY

OF ALOPECIA

T J Whitbread BSc. BVSc. MRCVS DipECVP Abbey Veterinary Services Devon

After qualifying from Liverpool in 1977, I spent a period of time in general mixed practice In Leicester where I developed an interest in dermatology before returning to Liverpool as a lecturer in veterinary pathology. At Liverpool, I gained extensive experience in diagnostic pathology, was involved in immunological research, looking at T- and B-cell activity and cell culture in a number of experimental situations, and was also involved in researching gastrointestinal diseases in dogs. I left Liverpool in 1985 to establish a diagnostic histopathology service at Bloxham Laboratories (which would eventually become Axiom Laboratories) and I subsequently set up Abbey Veterinary Services providing specialist diagnostic histopathology and cytology to the profession. I have continued to develop a special interest in dermatopathology and have been a board member of BVDSG and ESVD.

This is titled as an introduction and is intended as an overview of the pathology of alopecia in domestic species. We will look briefly at the hair cycle and its control, how, where and when to biopsy and look at the basic pathology of the most common conditions that give rise to clinical alopecia. I will try to concentrate on areas where pathologists find difficulties in interpretation so that you as clinicians can better interpret the pathology report.

Alopecia is one of the major problem areas for histopathologists and there are a number of potential reasons for this:

1. Histological changes in cases of alopecia are often not pathognemonic especially the non-inflammatory conditions

2. The changes can look very different depending upon the time course of the disease process

3. There have often been therapeutic interventions before biopsy and this can alter the histological picture

4. The clinical input for alopecia is perhaps more essential than other skin diseases

5. There are often secondary changes, which can sometimes become the dominant feature

Alopecic disease is often described has having atrophic follicles but true atrophy is very uncommon. True atrophy is a reduction in the overall size of the follicle but most alopecic conditions simply are caused by arrest of the hair follicle. In reports therefore I rarely use the descriptor “atrophy” but normally use the phrase follicle growth arrest.

NORMAL SKIN

Normal dog Normal cat

Normal horse Normal hamster

As you know hair growth is a cycle composed of 3 major phases. Each phase of the cycle has a number of different stages (Fig 1). Most skin pathology reports both for alopecic and for non-alopecic conditions will normally indicate the phases of the hair cycle seen in the sections. For alopecic cases of course the phase of the cycle can be important but it tends not to be as important in domestic species as in man. This is probably due to the fact that we do not fully understand the pathogenesis of alopecia in domestic species. The phase is certainly not as useful as as is often assumed (See Table 3 on page 67).

The length of each part of the cycle varies between species and has been modified by the genetic selection of domestic species so that different breeds also can have differing lengths of each stage of the cycle. Some species – man, Angora rabbits and Merino sheep have long, sometimes very long, growth phases (eight years in a Merino sheep). Some breeds of sheep such as the Romney may remain in anagen stage for the whole of its life.

Other species such as dogs, horse, most cats and hedgehogs have a short anagen phase and a relatively long telogen phase. Even that can vary with breed. In one study by Dunstan et al Beagles had 21% of their follicles in anagen phase whereas Poodles revealed 98% in anagen phase. As a general rule the longer the anagen phase, which is genetically determined, the longer the hair.

Fig 1. The hair cycle. Veterinary Dermatology VOLUME 23, ISSUE 3, pages 206-e44, 11 MAY 2012

FEATURES TO NOTE:

1. Changes are restricted to the lower half of the follicle

2. Hair growth is thought to be controlled and initiated by stem cells in the mid part of the follicle. In some species there is a distinct bulge at this site and is therefore logically described as the bulge region but in some species a bulge is not present but similar cells are assumed to be active in that area

3. The shedding of the hair (exogen) is an active process probably involving protease activity within the trichilemmal keratin. The hair is not simply pushed out by the new emerging hair

4. A relatively new phase has been suggested – Kenogen – this is essentially hairless telogen

5. Trichilemmal keratinisation occurs at the end of the catagen phase and into telogen and this “welds” the hair shaft into the now shortened and inactive follicle. This then waits for exogen and the cycle to start again

6. Note the levels within the dermis that the follicle reaches in the different phases

Telogen Kenogen Early anagen Late anagen

Early catagen Late catagen Indeterminate Indeterminate

Veterinary Dermatology VOLUME 23, ISSUE 3, pages 206-e44, 11 MAY 2012

The follicle arrangement and sizes of hairs are also species variable. A pattern retained in most mammals however has a central large primary hair and a smaller secondary hair on either side. There are then also a variable number of small secondary hairs (wool fibres)

THE NORMAL HAIR FOLLICLE

The hair follicle can be considered as a number of tubes one inside the other all developing from the deep hair bulb.

FEATURES TO NOTE:

1. The hair follicle papilla is of connective tissue origin.

2. The papilla and the perifollicular connective tissue are very important in the control of the follicle development

3. The IRS is thinner and densely stained

4. The ORS is thicker with vacuolated cells

5. The Henle and Huxley layers are two of the three layers of the IRS

6. The Glassy membrane is more prominent in some breeds than others

CONTROL OF FOLLICLE GROWTH

The two areas of the hair follicle that control follicle growth are the dermal papilla which arises from the mesenchyme and the stem cells that are situated in the follicle sheath at the attachment of the arrector muscle. As indicated already, in some species (man and mice) there is actually an enlargement of this area called the “bulge”. This is not present in our domestic species but I will use the term “bulge” to indicate the stem cells within the follicle sheath.

The mechanism of control of the dermal papilla and the bulge stem cells is not fully understood. The dermal papilla cells do not change a great deal during the hair cycle, but the proteoglycans matrix in the papilla does appear to alter during certain phases of the hair cycle and this may be important in the overall control of the follicle growth. The perifollicular fibrous matrix around the lower part of the hair follicle and the hair bulb may also contribute factors influencing growth.

Control of follicle growth and, hence, the control of the whole of the hair cycle is extremely complex and I include here only small notes to show the complexity.

TABLE 1 Examples of Extrinsic and Intrinsic Growth Factors Affecting the Murine Hair Follicle

Category Examples Extrinsic Factors Endocrine Androgens, oestrogens, thyroid hormones, cortisol, prolactin, melatonin Neural Neuropeptides, catecholamines, neurotrophins Immunologic Mast cells, macrophages Miscellaneous Oxygen, nutrients (iron, zinc, vitamins etc).

Intrinsic Factors Cytokines/growth factors TGF-/bone morphogenetic protein family, fibroblast growth factor family, interleukin-1, insulin growth factor family, neutrophins, platelet-derived growth factor, epidermal growth factor, TGF, hepatocyte growth factor Hormones Dihydrotestosterone, parathyroid hormone reactive peptide paracrine/autocrine) Neuropeptides ACTH Adhesion molecules Neural cell adhesion molecule, intercellular adhesion molecules, E- cadherin, P-cadherin, intergrins Homeobox genes Hox, Pax, Msx Transcription factors Hairless, winged-helix nude, lymphoid enhancer binding factor Enzymes Protease/antiprotease system: collagenases, phosphates, endonucleases, telomerases, caspases

Adapted from Paus et al. JID 4:338-345, 1999

TABLE 2 Intrinsic Factors Affecting the Murine Hair Cycle

Category Inhibitors of the Hair Cycle Stimulators of the Hair Cycle Anagen inhibition and/or catagen (Anagen induction, promotion, induction and/or telogen prolongation and/or catagen inhibition) prolongation) Hormones Cortisol ACTH Oestrogen Thyroid hormones Corticotropin-releasing hormone ACTH Melatonin Prolactin Growth Brain-derived neurotrophic factor Fibroblast growth factor 7 Factor Bone morphogenetic protein-4 Hepatocyte growth factor/scatter factor Epidermal growth factor Insulin-like growth factor-1 Fibroblast growth factor Sonic hedgehog Neurotrophin-3,4 TGF-, B1 Cytokines Interleukin-1-6 Substance P

Adapted from Paus et al. JID 4:338-345, 1999

The full interaction of all of the factors is not fully understood. The factors are both extrinsic and intrinsic and it is predominantly the extrinsic factors that we are dealing with clinically; these are mainly the hormones. These factors can affect the hair cycle in a number of different ways in order to produce the alopecia. We can, for example, have anagen inhibition, catagen induction or telogen prolongation, all of which will lead to alopecia, and all of which will tend to lead to the same histological pattern of a predominance of telogen follicles. Some factors may have more than one effect, for example, thyroid hormone can induce anagen but can also increase the length of the anagen phase. For an indication of the factors involved in the control of follicle growth see Tables 1 and 2.

BIOPSY

Before biopsying any skin lesion a list of differential diagnoses should always be prepared. The biopsy is a rule-out as well as a rule-in. Sample and choice of sample site and number of samples is better informed with a differential list. It is also necessary to try to establish which lesions are primary and which are secondary. Biopsies should be as representative of the clinical picture as possible. Always include that list with your submission to the lab. I find it the most important piece of information, as it is essentially a shorthand history.

For alopecic lesions biopsies should be taken from the centre of the alopecic area which is the area of maximum change to the hair cycle and lesions here are therefore more fully developed. Other biopsies should include the leading edge of a developing lesion at the junction with normal skin and on some occasions biopsies from an adjacent normal area of skin can be useful.

Obviously there is a limit to the number of biopsies that can be taken from a particular area in any single case. Six 6mm or 8mm punch biopsies are often recommended for most skin conditions except the vesiculobullous diseases which usually require ellipse/wedge biopsies in order to prevent rupture of the vesicles. The leading edge biopsies can often be considered a bonus but if we are dealing with a transient inflammatory process such as sebaceous adenitis the leading edge will have the most active lesion and therefore may be the more diagnostic sample. Lesions of sebaceous adenitis and alopecia areata usually do not look inflamed.

A biopsy from clinically normal adjacent skin can be useful for comparison of follicle sizes and growth and it is also sometimes the case that clinically normal skin actually is lesional histologically. Unless the lesion is on the ventral abdomen or inside the thighs avoid biopsying these sites as even in normal dogs these areas have poor follicle growth.

Before removal of the biopsy the surface should be marked with an indelible marker by a line in the direction of the flow of the hairs. This enables the laboratory to trim the biopsy (usually punches are halved) so that the sections are cut longitudinally along the follicle. This is the way that pathologists are most used to looking at follicles.

You may have seen discussions of sectioning follicles transversely at differing levels along the follicle. This is a technique used in human medicine where they are most commonly looking at follicle density and ratios of the phases of hair growth, which are features that cannot be adequately judged with longitudinal sections. I have never personally found this

to be a useful technique in veterinary medicine but as far as I know none of us have used this technique consistently. In addition it is also very difficult to get TS sections at different levels of the follicle.

Bear in mind that cats have about 6,000-10,000 hairs per square centimetre and dogs have 1500-4000 per square centimetre. On an average 6mm punch biopsy section there are 4-6 follicles only depending on the site. We are therefore looking at a minute fraction of the follicles in an affected area and sometimes diagnostic lesions are not present because of this necessarily small sample size. Re-biopsy therefore may sometimes be necessary. This should not be considered a failure of the biopsy site choice or technique but may simply be due to the small sample of the follicles and the often patchy nature of the histological changes. This sometimes cannot be avoided.

NON-INFLAMMATORY ALOPECIA

I will concentrate on the non-inflammatory alopecias because they are the most problematic for histological diagnosis.

You can see from Table 3 that the phase of follicle growth arrest is not often helpful. Most follicles in the majority of non-inflammatory alopecias are in hairless telogen phase. We therefore have to look at other changes to attempt a diagnosis. I must caution however that a + or – sign in the table is not necessarily always accurate as these features indicated can show considerable variation between individuals and it is these that give rise to the difficulties with diagnosis. Each criterion is not usually diagnostic in itself but contributes to a multivariable system that produces a pattern. It is the overall pattern recognition that pathologists use to suggest a diagnosis.

Follicle Follicle Epidermis Flame Condition Phase Inflammation Atrophy Hype rplastic Normal Atrophy Follicles Comedones Hypersensitivity Hairless ++ - ++ + - - - - / Allergy Telogen Hypothyroidism Hairless + - + - - - - Telogen Canine HAC Hairless - + - + - + - - Telogen Feline HAC Hairless - + - - + - ++ + - Telogen Sertoli Cell Hairless + - + + - - - - Tumour Telogen Some catagen Alopecia X Hairless - - - + - ++ - Telogen Post Clipping Haired - - - + - ++ - Telogen Table 3 - There are no absolutes here. +- = maybe/sometimes

NOTES ON TABLE 3

HYPOTHYROIDISM

1. Can mimic other skin diseases

2. Very similar to changes in chronic dermatitis

3. Always inflamed; sometimes markedly. This can be associated with secondary infection, but often not.

4. Epidermal and follicle sheath hyperplasia usually marked.

5. The most difficult endocrinopathy to confirm and with better biochemical and endocrine tests, rarely biopsied.

6. Dermal mucinosis can be seen but extremely uncommon. Mucinosis is common in some breeds – Shar Pei and Chows

CANINE HYPERADRENOCORTICISM (HAC)

Severe follicle atrophy Dermal bone and fibrosis Inflammation and early calcification

1. Growth arrest accompanied by true follicle and adnexal atrophy – follicles are smaller and look very weedy

2. Small comedones common

3. Dermal calcification common – can become bone

4. May have central bright red trichilemmal keratinisation

5. Epidermis and especially follicle sheath much thinner than normal

6. The most frequent endocrinopathy to confirm on biopsy especially as other tests can be non diagnostic. Biopsy very useful for this condition

7. When there is calcification there is considerable inflammation

FELINE (HAC)

1. Similar to canine

2. Adnexal (follicles and glands) atrophy even more marked

3. Central trichilemmal keratinisation very, very characteristic

4. Dermis also very atrophic

5. Rare

FEMALE AND MALE HYPEROESTROGENISM

1. Can be inflamed as frequently infected

2. Not dissimilar to hypothyroidism

3. Some late catagen follicles

4. Thickened connective tissue sheath around catagen/telogen follicles

5. Biopsy considered not diagnostic but suggestive of endocrinopathy

6. The changes are the same for male (sertoli cell tumour) and female

CANINE AND FELINE DERMATITIS REACTION (ALLERGY)

See below under inflammatory alopecia

ALOPECIA X

1. Flame follicles are the key here and usually prominent

2. Strong breed association

3. Epidermis often normal thickness

4. In later stages follicles become distorted and dysplastic

POST CLIPPING ALOPECIA

1. Hair shafts are retained

2. Very pronounced trichilemmal keratinisation

3. True flame follicles are rare

4. May have clusters of secondary hair germ at the base (hook)

5. Rare anagen follicles

TELOGEN EFFLUVIUM

1. Follicles undergo synchronous anagen and therefore shed all at the same time

2. Associated with stress

3. Almost always biopsied late so follicles are all in anagen phase. This gives a normal appearing biopsy. It takes 2-3 months for the hairs to reach the surface

DYSPLASTIC CONDITIONS

CYCLIC/SEASONAL FLANK ALOPECIA

1. The most common cause of alopecia we see

2. Not included in table 3 and considered a dysplasia

3. Infundibular hyperkeratosis with extensions into the shortened and distorted inferior parts of the primary and secondary follicles – “Witches feet”

4. Occasionally a mild superficial dermatitis (not interface)

5. Often hairless dysplastic follicles and anagen follicles in the same biopsy

6. Biopsy is usually diagnostic.

COLOUR DILUTE ALOPECIA – BLACK HAIR FOLLICLE DYSPLASIA

1. Histologically these conditions are identical

2. Initially hair growth is normal with mixed anagen and telogen follicles

3. Later follicles in telogen phase

4. Later still follicles can be atrophic and dysplastic

5. Large clumps of melanin (macromelanosomes) present in hair bulb, shaft and free within follicular infundibulum is diagnostic

6. Very variable phenotypic expression. Can have typical histological changes but no clinical alopecia

CANINE PATTERN ALOPECIA

1. Follicles reduced in size – shorter, thinner with petite anagen hair bulb

2. Residual hair shafts are very fine

3. Often breed related distribution

INFLAMMATORY ALOPECIAS

This is too big a subject to detail here and these usually are much less of a diagnostic problem than non-inflammatory alopecias. Here are a few notes on common diseases or where the pathologist may have difficulty and therefore you may not get a specific or

accurate diagnosis from your biopsy. Any inflammatory process that causes destruction of the follicle will lead to alopecia. Also chronic inflammation in the skin, not necessarily directed at the follicles can switch the follicle off. Presumably the inflammation alters the environment (cytokines?) that affects the activity of the follicle cells.

CANINE AND FELINE DERMATITIS REACTION (ALLERGY)

1. Changes vary with chronicity

2. In early stages no follicle growth arrest

3. When chronic can be identical to hypothyroidism

4. Epidermis and follicle sheaths hyperplastic

5. Follicles can become distorted and dysplastic

ISCHAEMIC

1. Telogen follicles but very atrophic – faded

2. Smudged dermal collagen

3. Active vasculitis – very difficult to see in sections so often no inflammation

ALOPECIA AREATA

1. Affected follicles are often sparse and often not present in the sections

2. If negative on pathology get sections cut deeper or may need more biopsies

3. Inflammation concentrated around and in the hair bulb. Mostly lymphocytes

4. No other non-neoplastic condition causes inflammation within the hair bulb

5. Late stage – no inflammation – follicles small and distorted

SEBACEOUS ADENITIS

1. Histological pattern varies with breed

2. In late stage skin histologically is completely normal apart from the absence of sebaceous glands. This can easily be missed as absence of a feature is more easily missed than presence

3. Poodle invariably presented in late stage without active inflammation. Vizlas almost always still have some inflammation

4. Orthokeratotic hyperkeratosis is severe

MURAL FOLLICULITIS

1. This is not a diagnosis but a description

2. More specific diagnosis depends on the site of lymphocyte attack e.g. interface (exfoliative dermatitis), isthmus/mid follicle (pseudopelade)

3. Histiocytic or granulomatous mural folliculitis causes profound follicle growth arrest

4. Affects cats and dogs but rare

5. Biopsies are diagnostic

SCARRING ALOPECIA

Any severe damage to the skin that destroys most of the follicle will lead to scarring alopecia. The follicle cells are intimately involved in regeneration of skin tissue after injury.

ALOPECIA INVOLVING ORGANISMS

DEMODICOSIS

1. Straightforward histological diagnosis

2. However if there is only one mite in 2 or 3 biopsies is this significant?

3. Almost all cases where demodex are present in biopsies have been scraped negative!

4. Secondary bacterial infection not common

VIRUS INFECTIONS

1. Mainly in the cat (and rabbit) not significant as far as we know in the dog

2. Herpes does not significantly affect the follicles but pox does

3. Pox virus causes severe necrosis of the follicle with inclusions

4. Inflammation mainly eosinophils

DERMATOPHYTOSIS

1. False negative results not uncommon with all forms of testing

2. Inflammation can be mainly eosinophilic

BACTERIAL FOLLICULITIS

1. Very common both as primary and secondary infections

2. Usually also leads to furunculosis

3. With bacterial folliculitis and pyoderma bacteria are often not seen in sections but the pathologist assumes they are there

NEOPLASIA

1. Epitheliotropic lymphoma frequently infiltrates the follicles causing them to switch off

2. In some cases the follicles are the only epithelium affected

3. This is especially seen in Hamsters where it is the major cause of severe often complete alopecia

This has been an overview and an introduction. I hope it has provided you, as clinicians, with a background to the biology of the hair follicle and a very brief review of the salient features of the major conditions affecting the hair follicle. I have outlined the difficulties with the pathological interpretation of biopsies from areas of alopecia and this area of dermatopathology will remain problematic for a very long time to come.

If you are particularly interested in this area of dermatology, I would recommend two publications in which there are numerous references to original research. They are:

REFERENCES

Hair loss disorders in domestic animals (2009) Mecklenburg, Linek and Tobin (ISBN- 13:978-0-8138-1082-9)

Skin diseases of the dog and cat (2005) Gross, Ihrke, Walder, and Affolter (ISBN-10:0632-06452-8)

Small animal dermatology 7 th Ed. (2013) Miller, Griffin and Campbell. ISBN978-1-4160- 0028-0

Canine non-inflammatory alopecia, Muntener T, et al. Vet Dermatol, (2012), 23 206-10

OLLICULAR YSPLASIA F D

Manon Paradis, DMV, MScV, Dipl. ACVD, Department of clinical sciences, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.

INTRODUCTION

Follicular dysplasia encompasses a group of genetic, non-inflammatory dermatological disorders resulting in hair loss and altered coat quality. They include many ill-defined alopecic disorders that are either coat colour-linked (e.g., colour dilution alopecia, black hair follicular dysplasia) or non-coat colour-linked (e.g., canine recurrent flank alopecia, alopecia X and the various breed associated follicular dysplasias).

The goal of this presentation is to describe and discuss the clinical features, diagnosis and treatment of the different types of canine follicular dysplasias. For the ease of presentation, hair follicle dysplasias will be divided into those where hair follicle dysplasia is so severe that no hair shaft formation is seen at all, and those where hair shafts are formed by “dysplastic” hair follicles. The latter will be further sub-divided into colour-linked and non-coloured linked follicular dysplasia. Alopecia X will be discussed in the following presentation.

HAIR FOLLICLE DYSPLASIA WITHOUT HAIR SHAFT FORMATION

Hair follicle dysplasias without hair shaft formation are essentially all congenital disorders (i.e. present at birth).

CONGENITAL HYPOTRICHOSIS

Congenital hypotrichosis is the term used to describe dogs born with abnormal haircoat. Cases have been reported in several breeds and in mongrels. Some of those cases have not been sufficiently evaluated to determine whether other ectodermal defects were present.

ECTODERMAL DYSPLASIA

Describes a group of disorders characterized by abnormality in embryonic development and gives rise to mature structures that are deficient in number, size, character, or function such as skin and appendages (hair, nails and sweat glands) and teeth. Some ectodermal dysplasia cases are inherited as a X-linked recessive trait (i.e. seen predominantly in males).

CLINICAL FEATURES

Dogs with ectodermal dysplasia are born with a symmetrical alopecia typically affecting the fronto-temporal, sacral, abdominal and proximal limb regions. In addition to the alopecia, they have oligodontia (with peg-shaped teeth), and glandular (epitrichial and atrichial sweat, sebaceous, lacrimal, tracheal, and bronchial) aplasia.

DIAGNOSIS

Histopathological examination of skin biopsies reveals absence of hair follicles, arrector pili muscles, sebaceous and sweat (epitrichial and atrichial) glands. As opposed to human patients, these dogs do not suffer from hyperthermia because skin atrichial (eccrine) sweat glands are only located in footpads and have little thermoregulatory significance.

HAIRLESS BREEDS

The hairless breeds resulted from intentional breeding of an animal with a spontaneous genetic mutation. It is now known that the Chinese crested dog, the Mexican hairless dog (aka Xoloitzcuintli), and the hairless Peruvian dog all share the same mutation. The hairlessness is inherited as a monogenic autosomal semi-dominant trait linked to chromosome 17. Heterozygous dogs are hairless, and homozygous mutants die during embryogenesis.

The Mexican hairless dog dates back more than 3000 years, whereas the Chinese crested dog, which is now the most popular hairless breed, is a much more recent breed (late 1800’s). The haired (homozygous normal or “wild-type”) Chinese crested dog littermates have long fur and are known as “powderpuffs”. Hairless littermates are devoid of hair

except for the crown of the head, lower parts of the extremities and the tail. The haired (“wild-type”) Peruvian and Mexican hairless dogs have short haircoats. The phenotype of hairless dogs is now classified as canine ectodermal dysplasia because these dogs have missing or abnormally shaped teeth in addition to a sparse or absent hair coat.

Skin biopsy reveals rudimentary primary follicles with distended follicular infundibula. Mesenchymal condensation beneath cystic follicular infundibula suggests remnants of potential dermal papilla. The sweat glands are not affected. Adult hairless dogs often exhibit numerous comedones, most prominent on the dorsum, ventral neck, distal extremities, and prepuce with secondary bacterial folliculitis. Also, for obvious reasons, they are prone to actinic damage.

The American hairless terrier, which is a mutant of the American rat terrier, is not so well characterised but does appear to fall into the ectodermal defect category.

HAIR FOLLICLE DYSPLASIA WITH HAIR SHAFT FORMATION

Hair follicle dysplasias with hair shaft formation are essentially all acquired alopecias. These dogs are born with a normal hair coat, however, an acquired alopecia develops from as early as 3 months of age (e.g., black hair follicular dysplasia) to as late as over 10 years (e.g., some dogs with recurrent flank alopecia or Alopecia X).

This group of follicular dysplasias can be further divided histologically into categories in which there are abnormalities in the process of melanization of the pilosebaceous units (e.g., colour dilution alopecia) and those where the hair cycle is abnormal (e.g., canine recurrent flank alopecia, alopecia X).

COLOUR DILUTION ALOPECIA (CDA)

Colour dilution alopecia (formerly colour mutant alopecia), is an uncommon inherited disorder which causes tardive alopecia in some dogs with diluted (e.g., blue or fawn) hair coats.

AETIOPATHOGENESIS

CDA is a neuroectodermal dysplasia inherited as an autosomal recessive trait. It appears to be a disorder of melanosome transfer within the melanocyte but the aetiopathogenesis is still not fully understood.

Mutations in or near the melanophilin ( MLPH) gene are causing dilute coat colour in dogs (at least in Doberman, beagle and large Munsterlander). In dogs, coat colour dilution is unfortunately often accompanied by alopecia.

More than 20 breeds segregate for dilute coat colour. However, alopecia does not develop in all dogs with blue or fawn coats, and the frequency varies within affected breeds. The dilute mutation is required but not sufficient to develop alopecia. The risk to develop CDA appears to be breed specific and depends on other factors not yet determined. For example,

most (if not all) blue Dobermans will develop some degree of alopecia, while most Weimaraners won’t.

Dilute hairs have larger pigment granules than the non-dilute red or black hairs. The initial hair loss is due to hair shaft fracture at the point of melanin clumping (aggregated melanosomes), and secondary bacterial folliculitis further contributes to the hair loss. However, these are not usually sufficient to explain the extent of alopecia. It is possible that the melanin accumulation in bulbar melanocytes and large pigment clumps, which can separate the bulbar matrix cells, cause significant damage to the hair bulb or that the abnormal transfer of melanosomes in CDA results in a lack of stimulation of the hair bulb keratinocytes which may lead to resting, non-cycling follicles. Alternatively, an independent secondary disease process could be the cause of follicular inactivity.

CLINICAL FEATURES

CDA has been most widely recognised and reported in blue Doberman pinschers, but it also has been seen in several other breeds with dilute coat colours such as Dachshund, whippet, Italian Greyhound, Chow Chow, Yorkshire terrier, Chihuahua, and more recently in silver Labradors.

First clinical signs are usually noticed between 3 and 12 months of age, although some dogs with very mild coat colour dilution (e.g., steel blue) may present alopecia later in life.

Affected dogs show a progressive alopecia, scaling and comedones affecting only the dilute areas of the hair coat. Affected dogs are prone to secondary bacterial folliculitis, which may cause pruritus and aggravate the hair loss. Lesions are usually slowly progressive with age.

DIAGNOSIS

Breed predisposition and presence of alopecia restricted to the diluted areas are evocative of this disorder. Trichoscopic examination of plucked hairs shows numerous large, unevenly distributed, melanin clumping of irregular shape and sizes along the hair shafts. The bulging pigment clumps may cause distortion and fracture of the hair. It is important to note, however, that the presence of melanin clumping indicates the action of dilution genes and does not necessarily mean the animal has, or will develop, CDA.

Histological examination of skin biopsies from affected areas shows dilated, keratin filled hair follicles, and abnormal melanin aggregates in the epidermal and follicular basal cells, hair bulbs, hair shafts, and follicular lumen, and numerous peribulbar melanophages. With time, all follicular activity ceases and the follicles become dilated and cystic.

DIFFERENTIAL DIAGNOSIS

CDA is a non-inflammatory disorder which can mimic endocrine skin diseases. Endocrinopathies such as hypothyroidism as well as demodicosis should be considered as differential diagnosis, and all underlying causes of superficial folliculitis should also be considered when the latter is present.

TREATMENT

CDA is an incurable, genetically determined dermatosis. Affected dogs are healthy otherwise, with the exception of secondary pyoderma.

Keratomodulating and antiseptic shampoos and moisturisers may help to reduce the incidence of pyoderma and scaling. Pyoderma should be treated with systemic antibiotics as needed. Palliative therapy may be carried out with melatonin, retinoids or essential fatty acids to improve hair and skin conditions, although there are no studies documenting their efficacy.

Melatonin, used as a non-specific hair cycling inducer, has been reported anecdotally to be effective in promoting hair regrowth in 12 dogs (which included a few blue Doberman) with CDA (Vetderm Listserv survey). There is no information, however, on duration of the beneficial effect.

BLACK HAIR FOLLICULAR DYSPLASIA

Black hair follicular dysplasia (BHFD) is a rare disorder of early onset in which dogs lose hairs in the black areas of their hair coat.

AETIOPATHOGENESIS

BHFD is a familial disorder with an early onset, which is believed to be autosomal recessive. Recent studies have suggested that it has the same molecular defect as in CDA, supporting the premise that CDA and BHFD merely represent various forms of severity.

CLINICAL FEATURES

BHFD has been recognized in a variety of breeds such as Bearded collie, Saluki, Border collie, King Charles spaniel, Jack Russell terrier, Gordon setter as well as mixed-breed dogs.

Affected dogs are born normal but hair coat changes, noticed exclusively in the black-haired areas, are seen as early as 4 weeks of age. Initially, there is loss of lustre of the black hairs, followed by progressive hair loss until all black hairs are lost (as early as 9 months of age). Excessive scaling occurs in the affected areas. The hair loss is permanent.

DIFFERENTIAL DIAGNOSIS

The early onset, colour-linked alopecia makes the diagnosis straightforward in most cases. Demodicosis and dermatophytosis should be part of the differential diagnosis in some clinical presentations. In addition, other types of follicular dysplasias, such as CDA and follicular dysplasia of the adult black and red Doberman Pinschers could be included in the differential diagnosis, at least based on histopathological findings.

DIAGNOSIS

Skin biopsies of the affected black areas reveal clumped melanin in follicular basal cells and hair matrix cells. Large melanin aggregates are seen within the hair shafts. The follicles are dilated and filled with keratin, hair shaft fragments, and large clumps of free melanin. Numerous peribulbar melanophages are seen in the dermis. These pigmentary changes are similar but usually less pronounced than they are in CDA. BHFD has been reported in large Munsterlander puppies, although it would seem more appropriate to name it CDA since affected dogs are born with a grey and white coat (rather than black and white).

TREATMENT

No effective treatment has been reported for this genodermatosis. A therapeutic approach similar to that of CDA could be attempted.

BLACK- AND RED-COATED DOBERMAN PINSCHERS FOLLICULAR DYSPLASIA

A follicular dysplasia of red or black Doberman Pinschers (FDRBDP) has been reported by Miller in 1990. Alopecia occurs between 1 and 4 years of age and begins in the flank region and progresses slowly to involve the caudal dorsum and entire flank region. The hypotrichosis is apparently permanent.

These dogs share many histopathological features of CDA and BHFD. However, they do not have a dilute coat colour nor have pigmentary clumping in the epidermal melanocytes which is a feature of CDA.

Because Doberman pinschers are predisposed to CRFA, CDA, FDRBDP and hypothyroidism, and because these four disorders can share clinical resemblance, skin biopsies and a thyroid function evaluation should be performed in any Doberman with an undefined endocrine-type alopecia.

HAIR FOLLICLE DYSPLASIA IN WEIMARANERS

There is a distinct form of alopecia in Weimaraners that has been named “Follicular dysplasia of the Weimaraner”. A genetic defect is assumed but the underlying pathogenesis has not yet been elucidated.

Clinicopathological findings are almost identical to CDA, except that the degree of severity is milder, suggesting that it could be another variant of a neuroectodermal dysplasia of the follicular pigmentary unit.

Alopecia occurs in young adults of both gender, usually between 1 and 3 years of age. Alopecia involves the back, lateral and ventral thorax, flanks and abdomen, but spares the head and limbs. In the affected region, hair shafts break and follicles are prone to recurrent bacterial infection.

Plucked hair shafts from affected areas contain large aggregates of melanin. In contrast to normal Weimaraners, the aggregates are larger and more numerous, and accompanied by large circular cuticular defects. Histopathological examination of skin biopsies from affected areas bears many similarities to CDA, but findings are less severe. Hair bulbs and hair shafts show melanocytes with large aggregates of melanosomes. Many hair follicles are distorted by large amounts of infundibular keratin.

CANINE FOLLICULAR LIPIDOSIS

This is a rare and presumably hereditary disease of hair follicles that develops within the first months after birth for which the underlying pathogenesis is unknown.

CLINICAL FEATURES

This disease has only been described in young Rottweilers. Anecdotal cases have also been seen in other breeds (Julie Yager, personal communication). It is characterized by early onset alopecia, affecting mahogany-coloured areas on the feet and face.

DIAGNOSIS

Follicular lipidosis is characterized on histopathological examination by intracytoplasmic lipid-filled vacuoles within cells of the hair follicle matrix. Similar vacuoles may be seen in the hair shaft. Alopecia is most likely a result of increased hair shaft fragility.

CANINE RECURRENT FLANK ALOPECIA

Canine recurrent flank alopecia (CRFA) is characterized by episodes of truncal alopecia that often reoccur on a yearly basis.

PATHOGENESIS

The high incidence in some breeds and the familial character of CRFA suggest a genetic influence although the specific cause remains obscure. The seasonal nature and recurrence suggests that photoperiod may be involved. There is a higher incidence of CRFA at higher latitude (around or north of the 45° parallel). In Australia and New Zealand, the onset of CRFA appears to be the reverse of what we see in the northern hemisphere (but also during their short photoperiod season) supporting a link of light exposure to this disorder. Exposure to abnormally long photoperiods (i.e. several extra-hours of artificial light) associated with indoor housing (common in dogs from colder climate) would result in a decrease of endogenous melatonin secretion.

Recently, Vandenabeele has shown systemic rather than local factors with effect on specific hair follicles. This was demonstrated by skin transplants of CRFA affected dogs on athymic

nude mice that showed normal hair growth in the transplanted skin (whereas the donor site still showed alopecia).

Studies on fibroblast growth factor-18 (FGF-18) did not support the hypothesis that an increase in this growth factor precedes initiation of anagen phase in dogs (as it has been noted in people recovering from alopecia areata).

CLINICAL SIGNS

CRFA is characterized by a fairly abrupt onset of non-scarring alopecia, usually bilaterally symmetric, with well-demarcated borders and often markedly hyperpigmented alopecic skin. The alopecia is usually confined to the thoracolumbar region but occasionally this is seen in association with alopecia on the dorsum of the nose, base of the ears, base of tail and perineum.

Spontaneous regrowth of a normal pelage occurs in 3 to 8 months (range: 1 to 14 months) although some individuals grow hair of a different colour in previously-affected areas (e.g., melanotrichia in Boxers and aurotrichia in miniature Schnauzers). In a few dogs, hair regrowth may become less complete after several yearly episodes; it may even progress to a permanent flank alopecia and marked hyperpigmentation. Approximately 20% of CRFA cases may have only one isolated episode of flank alopecia during their life; however, most dogs will develop recurrent alopecic episodes for years. Some dogs have an occasional year when the alopecia does not recur. The degree of alopecia is variable, with some dogs developing a virtually identical hair loss (size and duration) year after year, and other dogs developing larger areas and/or longer episodes of hair loss as years go by. Lesions may be more seasonal in northern climates than in equatorial regions.

Rarely, alopecia at the bridge of the nose, the base of the ears, the base of the tail and/or the perineum, which also manifest a spontaneous regrowth and recurrence, have been observed in conjunction with thoracolumbar alopecia in some breeds such as Airedales, golden retrievers, griffon Korthals, Dobermans, wire-haired pointers, and giant Schnauzers. Another atypical presentation was recently reported by Vandenabeele in a cane Corso dog showing recurrent alopecia restricted to the face and ears.

The mean age at the onset of the first episode is approximately 4 years (range: 8 months to 11 years). The majority of dogs have an onset of alopecia between November and March in the Northern hemisphere. Dogs of either sex and of all reproductive status can be affected. Several breeds are at higher risk of developing CRFA with Boxers accounting for approximately half of all cases. It appears to be rare to absent in the plush-coat Nordic breeds, German Shepherd Dog, and Cocker Spaniel.

Rachid reported CRFA in nine Boxers with concomitant non-pruritic, multifocal annular crusted lesions confined to the alopecic areas. Histopathologically, the inflammatory lesions were characterized as interface dermatitis. The alopecia and the interface dermatitis ran parallel courses of spontaneous remission and recurrence, or persistence, respectively. The relationship between the two histological reaction patterns is not known.

DIAGNOSIS

For most cases of CRFA, the diagnosis is based on signalment, history and clinical signs. Histopathological findings (such as “witches feet” and hypermelanosis of the sebaceous gland) are supportive of but not pathognomonic for CRFA.

In a dog presented at the first episode, other causes of alopecia such as endocrinopathies (e.g., hypothyroidism, HAC) or other follicular dysplasias need to be ruled out. Hypothyroidism remains an important differential diagnosis for CRFA (due to its frequency, and breed and age overlap). Moreover, hypothyroidism and CRFA have been diagnosed concurrently in a few dogs.

TREATMENT

The unpredictable course of CRFA and the spontaneous regrowth of hair render the evaluation of any therapeutic agent difficult, whether used to prevent CRFA or to shorten an existing episode of alopecia. Oral melatonin can be administered before or shortly after the onset of alopecia. Dogs affected with CRFA appear healthy otherwise, and benign neglect is also a valuable therapeutic approach.

BREED SPECIFIC FOLLICULAR DYSPLASIAS

Non colour-linked follicular dysplasias have been described in the Irish water spaniel, Portuguese water dog, Chesapeake Bay retriever and Pont Audemer spaniel.

AETIOPATHOGENESIS

It is unknown whether these breed specific follicular dysplasias share the same genetic defect or if they are distinct entities. It is at least plausible that the Chesapeake Bay retriever and the Irish water spaniel follicular dysplasias are the same since the Irish water spaniel is one of the several breeds used to create the Chesapeake Bay retriever.

Portuguese water dog follicular dysplasia is characterized by a symmetrical truncal alopecia which occurs in males or females, black or brown coated, and predominantly in dogs with curly rather than wavy hair coat. In general, the hair loss, which has a familial tendency, first occurs in young adults and involved the flanks or saddle region. Several episodes of alopecia and spontaneous hair regrowth occur in most dogs, but the new hairs do not have the texture and quality of normal hairs. Eventually the alopecia becomes permanent. It has been suggested that the alopecia is due to a follicular dysplasia with abnormal melanization of the pilosebaceous units.

Irish water spaniel follicular dysplasia is characterized by an hypotrichosis or alopecia affecting the latero-caudal neck, flanks, dorsum, rump or caudal aspect of the thighs, in addition to the short coat on the ventral neck and the tail, which are special characteristics of the breed. Clinically, affected dogs seem to show different patterns of hair loss that are

evocative of canine pattern alopecia, follicular dysplasia of the Portuguese water dog, as well as CRFA.

A follicular dysplasia has been reported in the Husky , however, I personally consider this clinicopathological presentation no different from alopecia X.

DIAGNOSIS

Breed predisposition and clinical signs are suggestive of this condition. Histopathology reveals features similar to CRFA and follicular dysplasia associated with abnormal melanization, although the clinical findings described in these breeds may vary. Histology of skin specimens shows various degrees of follicular hyperkeratosis, numerous follicles in kenogen (hairless telogen follicle), melanin clumping and dysplastic hair follicles. In the Portuguese water dog follicular dysplasia, unique histopathologic findings have been described. They include prominent apoptosis of keratinocytes in the inner root sheath, and dissolution of the hair matrix of anagen follicles.

TREATMENT

These genetically based dermatoses are incurable. Affected dogs are healthy otherwise with the exception of secondary pyoderma. In some cases, melatonin and essential fatty acid supplementation may improve the coat quality and reduce the severity of the alopecia.

CONCLUSION

At this point in time, our understanding of follicular dysplasias is rather limited. Genome- wide association studies (GWAS) might shed some light on these disorders in a near future. GWAS have recently established the 3 major genes that together account for most coat phenotype in dogs. Fibroblast growth factor 5 (FGF5 ) is associated with long hair, keratin 17 ( KRT17) is associated with the degree of curl, and a variant in the R-spondin 2 gene (RSPO2) is associated with wiry coat and presence of “furnishings”, which include moustaches, eyebrows and increased hair on legs. Let’s hope that this technology will eventually help us understand the array of varied and seemingly complex follicular dysplasia phenotypes, and that genetic tests will be available in the foreseeable future.

REFERENCES

Beco, L., Fontaine, J., Gross, T.L. et al. Colour dilution alopecia in seven Dachshunds. A clinical study and the hereditary, microscopical and ultrastructural aspect of the disease. Vet Dermatol.1995; 7: 91–97.

Cadieu E et al. Coat variation in the domestic dog is governed by variants in three genes. Science 2009; 326;150.

Cerundolo R, Paradis M, Mecklenburg. Breed specific hair-cycle abnormalities. In: Mecklenburg L, Linek M, and Tobin DJ editors Hair loss disorders in domestic animals Wiley-Blackwell, Iowa. 2009 p. 169-175.

Cerundolo R, Lloyd DH, McNeil PE, Evans H. An analysis of factors underlying hypotrichosis and alopecia in Irish water Spaniels in the United Kingdom. Vet Derm 2000; 11: 107-122.

Cerundolo R, Maudlin EA, Goldschmidt MH, Beyerlein SL, Refsal KR, Oliver JW. Adult- onset hair loss in Chesapeake Bay retrievers: a clinical and histopathological study. Vet Dermatol. 2005 ; 16: 39-46.

Cieslowski D, Paradis M. Alopécie saisonnière canine. Médecin Vétérinaire du Québec. 1993; 23:98.

Curtis CF, Evans H, Lloyd DH. Investigation of reproductive and growth hormone status of dogs affected by idiopathic recurrent flank alopecia. J Sm Anim Pract.1996; 37: 417-422.

Fontaine J, Beco L, Paradis M. Alopécie récidivante des flancs: à propos de 12 cas chez le griffon Korthals. Point Vét 1998 ; 29: 445-449.

Gross TL, Ihrke P., Walder EJ, Affolter VK: Skin diseases of the dog and cat. Clinical and histopathologic diagnosis. 2nd ed. Blackwell Science. 2005.

Gross TL, Tenerio AP, Munn RJ, Hargis AM, Kline A. Follicular lipidosis in three Rottweilers Vet Dermatol. 1997;8: 33-39.

Guaguère E, Degorce-Rubiales F, Poujade A, Lecanu J, Petriowski M, Prélaud P.. Genetic follicular dysplasia in Pont Audemer spaniel dog: A report of eight cases. Vet Dermatol. 2000; 11 (s1): 14-40.

Hargis, A.M., Brignac, M., Al Bagdadi, F. et al. Black hair follicular dysplasia in black and white Saluki dogs: differentiation from colour mutant alopecia in the Doberman pinscher by microscopic examination of hairs. Vet Dermatol.1991; 2: 69–83.

Mecklenburg L, Cerundolo R, Paradis M. Breed-specific canine hair cycle abnormalities. Hair loss disorders in domestic animals. L. Mecklenburg, M. Linek, D.J. Tobin ed. Willey- Blackwell. 2009 pp. 169-175.

Mecklenburg L. An overview on congenital alopecia in domestic animals. Vet Dermatol. 2006;17:393-410.

Miller MA, Dunstan RW. Seasonal flank alopecia in boxers and Airedale terriers: 24 cases (1985-1992). JAVMA 1993, 203:1567-1572.

Miller WH, Scott DW. Follicular dysplasia of the Portuguese water dogs. Vet Dermatol. 1995; 6: 67-74.

Muntener T, Doherr MG, Guscetti F, Suter MM, Welle M. The canine hair cycle- a guide for the assessment of morphological and immunohistochemical criteria. Vet Dermatol. 2011;22: 383-395.

Muntener T, Schuephach-Regula G, Frank L, Rufenacht S and Welle M. Canine non- inflammatory alopecia: a comprehensive evaluation of common and distinguishing histological characteristics. Vet Dermatol. 2012; 23: 206-222.

Paradis M. An approach to symmetrical alopecia in the dog. In: British Small Animal Veterinary Association (BSAVA) Manual Canine and Feline Dermatology 3 rd edition. H. Jackson and R. Marsella Eds. 2012 pp. 91-102.

Paradis M. Canine recurrent flank alopecia. In: Mecklenburg L, Linek M, and Tobin DJ editors. Hair loss disorders in domestic animals. Wiley-Blackwell, Iowa. 2009. pp. 155-161.

Paradis M. Recurrent flank alopecia, canine. Clinical Veterinary Advisor Dogs and Cats. 3 rd edition. E. Coté ed. Mosby Elsevier. 2015 pp. 890-891

Paradis M. Canine follicular dysplasia. Clinical Veterinary Advisor Dogs and Cats. 3 rd edition. E. Coté ed. Mosby Elsevier. 2015 pp. 365.

Paradis M. Melatonin. Roundtable summaries. Derm Dialogue Winter 2002 2002, p 12-13.

Paradis M. Melatonin therapy in canine alopecia. Bonadura ED. In Kirk's Current Veterinary Therapy XIII. WB Saunders Philadelphia. 1999 pp. 546-549.

Paradis M, Cerundolo R. Genodermatosis: alopecia and hypotrichoses. Advances in Veterinary Dermatology Vol 5. Oxford: Bailliere Tindall; 2005 pp. 360–364.

Philipp U et al. Polymorphisms within the canine MLPH gene are associated with dilute coat color in dogs. BMC Genetics 2005, 6:34.

Rachid MA, Demaula CD, Scott DW, Miller WH, Senter DA, Myers S. Concurrent follicular dysplasia and interface dermatitis in Boxer dogs. Vet Dermatol. 2003;14: 159-166.

Roperto, F., Cerundulo, R., Restucci, B. et al. Colour dilution alopecia (CDA) in ten Yorkshire Terriers. Vet Dermatol. 1995; 6: 171-178.

Rothstein, E., Scott, D.W., Miller, W.H. et al. A retrospective study of dysplastic hair follicles and abnormal melanization in dogs with follicular dysplasia or endocrine skin disease. Vet Dermatol.1998; 9: 235–241.

Scott, D.W. Seasonal flank alopecia in ovariohysterectomized dogs. The Cornell Vet 1990; 80: 187-195.

Shanley KJ, Miller WH. Adult onset growth hormone deficiency in siblings Airedale terriers. Comp Continuing Educ Pract Vet 1987; 9: 1076-1082.

Vandenabeele SI, DeCock H, Van Ham L, Meyer E, Daminet S. Study of the behaviour of lesional and nonlesional skin of canine recurrent flank alopecia transplanted to athymic nude mice. Vet Dermatol. 2013;24: 507-511.

Vandenabeele SIJ, Daminet S, Van Ham L, Farver TB, Decock HEV. Immunohistochemical evaluation of fibroblast growth factor 18 in canine recurrent flank alopecia. Vet Dermatol. 2012;23: 461-462.

Vandenabeele SIJS, Daminet SS, Van Ham LL, Farver TBT, DeCock HEV. Immunohistochemical localization of fibroblast growth factor 18 in hair follicles of healthy beagle dogs. Vet Dermatol. 2011;22: 423-428.

Vandenabeele SIJ, Declercq J, Daminet S, Schwarzkopf I, De Cock HEV. Atypical canine recurrent alopecia. Vet Dermatol. 2014;25 : 56-58.

Von Bomhard W et al. Black hair follicular dysplasia in Large Münsterländer dogs: clinical, histological and ultrastructural features. Vet Dermatol. 2006;17:182-188.

Waldman L. Seasonal flank alopecia in affenpinschers. J Sm Anim Pract 1995; 36: 272-273.

Wiener DJ. Clinical and histological characterization of hair coat and glandular tissue of Chinese crested dogs. Vet Dermatol 2013; 24: 274–281.

IMMUNE – MEDIATED ALOPECIAS

Manon Paradis, DMV, MScV, Dipl. ACVD, Department of clinical sciences, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.

INTRODUCTION

There are several immune-mediated dermatopathies causing alopecia in dogs. The aim of this presentation is to provide the clinician with an overview of selected immune-mediated skin disorders causing alopecia. These include sebaceous adenitis, dermatomyositis, post- rabies vaccine alopecia, adult onset generalized ischemic dermatopathy, alopecia areata (pelade) and isthmic lymphocytic mural folliculitis (pseudopelade).

SEBACEOUS ADENITIS

Sebaceous adenitis is an uncommon idiopathic skin disease in the dog.

AETIOPATHOGENESIS

The exact aetiopathogenesis of this disease remains unknown. A genetically inherited cell- mediated immune reaction directed against a component of the sebaceous glands is suspected. Another theory is that the initial defect could be an abnormality in cutaneous lipid metabolism.

The common feature of the disease is an inflammatory infiltrate affecting the sebaceous glands resulting in their destruction. Alopecia occurs by hair shafts breaking easily, most likely due to a decreased amount of sebum produced by the sebaceous glands.

CLINICAL FEATURES

Sebaceous adenitis is most commonly seen in standard poodles and Akitas but has been diagnosed in various other breeds including Vizsla, German shepherd dog, Hovawart, Lhasa apso, Bernese mountain dog, and mongrels. Young adult to middle-aged dogs are most commonly affected. No sex predilection has been reported.

There is a marked variability of clinical presentation depending on individual breeds and severity. Follicular casts (white scales adherent to hair shafts) is a common feature. They most likely result from the lack of sebum in the hair follicle infundibulum, where epidermis- like keratinization and desquamation occur.

In long-coated dogs (e.g., standard poodles, Akitas) the first sign of disease is follicular casts protruding from the hair follicle. When hairs are plucked, the follicular keratinaceous debris

cast the root of the hair shafts. In standard poodles, the disease starts most often on the dorsal muzzle and temporal region, spreading to the dorsal neck and thorax, whereas in Akitas the alopecia is typically more extensive. Broken hair shafts, dull and brittle hair coat, excessive scaling, change in hair colour, and musty odour may be seen. Pruritus is variable but may be marked, especially if secondary bacterial or yeast infection is present. In the Akita, where the disease can be more severe, fever, anorexia, and lethargy have been reported.

In short-coated dogs such as the Vizsla, clinical presentation consist of coalescing patches of scaly alopecia with adherent scales developing more commonly on the face, head, and trunk.

DIAGNOSIS

Presence of follicular casts and alopecia in a susceptible breed is highly suggestive of the disease. Skin biopsy and histopathological examination is necessary to confirm the diagnosis.

In the early phase, dermatohistopathological changes are characterized by discrete perifollicular inflammation at the isthmus level of hair follicles. Later, nodular, granulomatous to pyogranulomatous inflammatory reaction around the sebaceous glands is seen. In addition, orthokeratotic hyperkeratosis and follicular plugging is observed in long- coated breeds. These hyperkeratotic changes tend to be milder in short-coated breeds. In advanced stages of the disease, the sebaceous glands are completely destroyed and the inflammatory reaction may disappear. Telogenization of hair follicles or follicular atrophy may occur. Suppurative folliculitis or furunculosis can be found when secondary staphylococcal infection is present.

Skin scrapings and hair plucks (trichoscopy) are useful for ruling out ectoparasites. Casts of keratosebaceous material adherent to hair shafts can be seen on trichoscopic examination, which is suggestive of sebaceous adenitis, particularly in the absence of Demodex mites. Cytologic examination to assess for presence of secondary bacterial or Malassezia infection, and Wood’s lamp and dermatophyte culture to rule out dermatophytosis may also be required.

DIFFERENTIAL DIAGNOSIS

Secondary sebaceous gland destruction with similar clinical hyperkeratosis can also occur with demodicosis, leishmaniasis, and severe granulomatous and histiocytic folliculitis. Differential diagnosis also includes dermatophytosis, bacterial folliculitis and various cornification disorders such as ichthyosis.

TREATMENT

Topical treatment with oil soaks, humectants (propylene glycol 50-75%) and shampoos are often effective but quite laborious. Oral cyclosporine (5 mg/kg q24h) has been shown to improve the clinical signs and to reduce inflammation greatly, as well has achieving

regeneration of sebaceous glands. It is, however, an expensive treatment option. There is evidence of a synergistic benefit on both scaling and alopecia if topical therapy is combined with oral cyclosporine. Isotretinoin has been reported to be effective in Vizsla. However, it is difficult to comprehend why considering they are known to reduce sebaceous gland size and decrease sebum secretion.

DERMATOMYOSITIS

Canine dermatomyositis is a hereditary, idiopathic inflammatory skin and muscle disease well-characterized in Collies and Shetland Sheepdogs.

AETIOPATHOGENESIS

Aetiopathogenesis of dermatomyositis is still unknown, although an autosomal dominant mode of inheritance with variable expression has been proposed. In Shetland Sheepdogs, inheritance of dermatomyositis has been linked to canine chromosome 35.

An immune-mediated or autoimmune basis is possible but it is unclear if immune reaction is the cause of the disease or is in response to pre-existing muscle or skin damage. Lesions could be induced by drugs, vaccines, infection (especially viral), toxins, internal disease, but causal relationship is unproven. Mechanical trauma and sunlight (UV), and reproductive stress (estrus, parturition, and lactation) may worsen the lesions.

Vascular lesions and local ischemia appear to play a central role in disease process, explaining the distribution of lesions which occur at pressure points and areas of low sustained circulation (ear and tail tips).

CLINICAL FEATURES

A familial basis as been reported in collies, Shetland sheepdogs, Beauceron shepherds; however, the disease has been diagnosed in many other breeds including Australian cattle dog, Welsh corgis, and chow chow.

Clinical signs are usually first noticed in dogs less than 6 months, and as early as 7 weeks of age. They wax and wane and vary from minor skin lesions (patchy alopecia, rarely vesicles) to severe ulceration of the skin, with a generalized debilitating myositis affecting the head and distal limbs.

Skin lesions are generally characterized by alopecia, erosions and crusting around the eyes, on the bridge of the nose, pinnae, bony prominences (elbows, hocks, digits), and the tail tip. Vesicles and ulceration may be seen. Some dogs also present with onychodystrophy. Pruritus is normally absent unless complicated by another condition such as pyoderma.

Many dogs show some degree of skeletal muscle involvement that can vary from subtle atrophy of temporal and masseter muscle to generalized muscular atrophy with megaesophagus and lameness.

DIAGNOSIS

Young dogs presenting with alopecia and crusting on face, pinnae, and tail tip along with muscle wasting in a predisposed breed (e.g., collie, Shetland sheepdog) is highly suggestive of dermatomyositis.

Initial data base may include skin cytological examination to rule out pyoderma and/or Malassezia overgrowth, skin scrapings to rule out demodicosis, and Wood’s lamp and fungal culture to rule out dermatophytosis. Serum biochemistry profile may show elevated creatine kinase. CBC and urinalysis results are usually unremarkable.

Histopathological evaluation of skin biopsy is characterised by hydropic degeneration in the basal cell layer and cell-poor lymphohistiocytic interface dermatitis. Follicular atrophy may be noted in chronic lesions. Vasculitis is occasionally seen.

DIFFERENTIAL DIAGNOSIS

Differential diagnosis includes demodicosis, dermatophytosis, bacterial folliculitis, Malassezia dermatitis, discoid lupus erythematosus, and vasculitis, and adult-onset generalized ischemic vasculopathy.

TREATMENT

The lesions wax and wane and response to therapy is difficult to evaluate. For acute flares, prednisone 1 mg/kg q24h, weaning down to an alternate-day regimen based on a favorable response is recommended. Prednisone can be used in conjunction with pentoxifylline (25 mg/kg q12h) for severe acute flares. Focal lesions can be treated with topical 0.1% tacrolimus.

Chronic management includes pentoxifylline (25 mg/kg q12h) alone, Vitamin E 200-800 IU/12h, oral cyclosporine, topical tacrolimus, and/or oral tetracycline and niacinamide (250 mg q8h PO for dogs < 10 kg or 500 mg q8h PO for dogs > 10 kg of each drug given for a minimum of 3 months, weaning down based on a favourable response). Flares can be minimized by avoidance of sunlight. Affected dogs should be neutered.

POST-RABIES VACCINE ALOPECIA

Localized or generalized ischemic vasculopathy may result from rabies vaccine administration.

AETIOPATHOGENESIS

The causal pathomechanism remains unknown, but it is likely that the formation of rabies antigen-antibody complexes that become lodged in vessel walls (a type III hypersensitivity response) is involved. Rabies viral antigen has been demonstrated in vessels and in the epithelium of hair follicles.

CLINICAL FEATURES

Rabies vaccine-associated ischemic dermatopathy is usually seen in adult dogs. It is typically seen in small breeds such as miniature poodle, Bichon Frisé, Shih Tzu, Lhasa Apso, Maltese, Yorkshire terrier, and Chihuahua.

The onset of clinical signs is typically 2 to 3 months after vaccine administration, but occasionally takes longer to develop. It usually consists in a focal alopecic lesion at the site of vaccine-administration, but occasionally can be widespread (see adult-onset generalized ischemic dermatopathy). The local form typically occurs over the shoulders, back or the posterolateral thighs and is characterized by a firm circular patch of erythema and alopecia. Old lesions often have a shiny appearance with mild scaling.

DIAGNOSIS

Histopathological changes are characterized by nodular perivascular accumulations of lymphocytes, plasma cells, and histiocytes in the deep dermis and panniculus. Macrophages occasionally contain cytoplasmic basophilic material that is believed to be phagocytosed vaccine product. The dermal changes also include moderate to severe follicular atrophy, hyalinization of collagen, mild interface dermatitis and mural folliculitis. These changes are often accompanied by cell-poor vasculitis (often quite subtle) of small blood vessels in the panniculus and the deep dermis.

TREATMENT

This localized form of ischemic dermatopathy does not necessarily require therapy. If inflammation is prominent, short course of glucocorticoids may be used. Pentoxifylline (25 mg/kg q12h) in combination with vitamin E (200 to 800 IU q12h) also can be used if needed.

ADULT-ONSET GENERALIZED ISCHEMIC DERMATOPATHY (rabies vaccine- induced or idiopathic)

CLINICAL FEATURES

Post-rabies vaccination alopecia associated with concurrent multifocal ischemic dermatopathy can rarely occur. Clinically, it emulates canine dermatomyositis, suggesting that the disease is caused by local ischemia of skin regions that are prone to impaired circulation. The main difference is the older age of onset. A similar clinical manifestation has been reported in Jack Russell terriers with no obvious history of previous vaccination.

In rabies vaccine-induced generalized ischemic dermatopathy, multifocal skin lesions develop within a few months after the appearance of the initial skin lesion at the injection site. However, some dogs never develop a lesion at the injection site. Lesions consist in alopecia, crusting, hyperpigmentation, erosions, and ulcers on the pinnal margins, periocular

areas, skin overlying boney prominences, tip of the tail, and paw pads. Lingual erosions and ulcers can also been seen.

DIAGNOSIS

The dermatohistological changes observed are indistinguishable from those observed in canine dermatomyositis, suggesting a common aetiopathogenesis of immunological damage to the vessels, resulting in ischemic damage to susceptible tissue. In addition, an atrophic, ischemic myopathy paralleling the onset of skin disease can also be seen.

TREATMENT

The generalized form of ischemic dermatopathy requires systemic therapy. As for dermatomyositis, pentoxifylline (25 mg/kg q12h) or prednisone (1 mg/kg q24h) can be used. Dapsone (1 mg/kg q8h) has also been recommended. Some patients may need a more aggressive immunosuppressive therapy with higher doses of prednisone, cyclophosphamide or azathioprine.

ALOPECIA AREATA (Pelade)

Alopecia areata is rare in dogs, in contrast to humans where it is a relatively common disease.

AETIOPATHOGENESIS

It is believed that the hair bulb melanocyte is a target cell population. Deposition of both immunoglobulin (particularly IgG) and complement around hair follicles, and the presence of circulating IgM and IgG to hair follicle-specific antigens have been documented. However, the pathogenic potential of anti-hair follicle autoantibodies in canine alopecia areata remains unclear.

CLINICAL FEATURES

Age of onset is highly variable, ranging from one to 11 years. Dachshunds appear predisposed.

Lesions usually consist of spontaneously arising and well-demarcated alopecic patches developing first on the head (muzzle, chin, forehead, peri-ocular, ears) and occasionally on the legs. Facial lesions usually exhibit a bilateral symmetry. In some cases, alopecia can progress to a more generalized distribution. In multicoloured-coated dogs, alopecia usually occurs first in dark brown or black areas (preferentially targeting pigmented hair).

Spontaneous and complete hair regrowth occurs in many dogs. Such regrowth is commonly of white hair, a feature also seen in humans and rodents with alopecia areata. In humans, in

100

the more extensive forms of the disease (alopecia totalis and alopecia universalis), spontaneous remission is rare.

DIAGNOSIS

Histopathological examination of skin biopsies is required to confirm the diagnosis. The histological hallmark is the so-called “swarm of bees” consisting of a mild to marked mononuclear cell infiltrate, predominantly composed of T-lymphocytes, focusing in (bulbitis) and around (peribulbitis) the anagen hair bulb. As with alopecia areata in humans, T-cells infiltrating the hair bulb epithelium itself are more commonly CD8+, while CD4+ cells predominate in the peribulbar region.

DIFFERENTIAL DIAGNOSIS

Differential diagnosis includes demodicosis, dermatophytosis, bacterial folliculitis, isthmic mural lymphocytic folliculitis (pseudopelade), ischemic alopecias such as dermatomyositis and rabies vaccine-associated alopecia, and vitiligo.

TREATMENT

Oral cyclosporine administration appears to be effective in dogs with alopecia areata.

ISTHMIC LYMPHOCYTIC MURAL FOLLICULITIS (Pseudopelade)

Isthmic lymphocytic mural folliculitis is a very rare immune-mediated disease in dogs.

AETIOPATHOGENESIS

Isthmic lymphocytic mural folliculitis in dogs bears some clinicopathological resemblance to pseudopelade of Brocq in humans which is characterized by a slowly progressive cicatricial alopecia and to the clinical similarity (pseudo) to alopecia areata (pelade) hence the term pseudopelade. However, since “pseudopelade” in humans represents the end stage of several diseases and thus is an ill-defined term, it has been suggested to use the descriptive term of “isthmic lymphocytic mural folliculitis”.

Of note, canine isthmic mural folliculitis can also be observed in conjunction with demodicosis, dermatophytosis and sebaceous adenitis.

As for alopecia areata, it is unknown whether the occurrence of autoantibodies to keratinocyte proteins is a primary or a secondary event in the pathogenesis of this disease.

Recently, a non-infectious, mural, mucinotic, isthmus folliculitis alopecia has been reported in Norwegian puffin dogs (lundehunds). It is characterized by a multifocal or serpiginous alopecia, follicular plugging, dry skin, slight scaling and pruritus. A lymphoplasmacytic, mural, isthmus folliculitis/perifolliculitis with follicular and perifollicular mucin was

101

observed on histopathological examination of skin biopsies. Inflammation did not involve the hair bulb but sometimes extended to the sebaceous glands, resulting in atrophy and absence of glands. Spontaneous remission was rare.

CLINICAL FEATURES

Clinically, the disease is characterized by gradually progressing non-pruritic, non- inflammatory focal or multifocal well-demarcated patches of alopecia. Scales and hyperpigmentation may be present. Spontaneous hair regrowth may be observed except for the syndrome observed in lundehunds.

DIAGNOSIS

The major histological finding is a mild to marked predominantly lymphocytic infiltration targeting the mid hair follicle (isthmus) sections. A perifollicular mononuclear infiltrate is also present around the isthmus. In late stage lesions severe follicular atrophy and variable atrophy of sebaceous glands, and sparse inflammation is seen. In lundehunds, follicular and perifollicular mucin is also observed.

DIFFERENTIAL DIAGNOSIS

Differential diagnosis includes demodicosis, dermatophytosis, bacterial folliculitis, alopecia areata, ischemic alopecias such as dermatomyositis and rabies vaccine-associated alopecia.

TREATMENT

Due to the small number of cases that have been described in the scientific literature, there is no established therapy for isthmic mural folliculitis in dogs. Cyclosporine was shown to be effective for this disease.

In the mucinotic, isthmus folliculitis of the lundehunds, oral prednisolone reduced pruritus but was not effective in resolving clinical lesions. However, all dogs treated with ciclosporin went into remission.

REFERENCES

Bergvall K, Shokrai A. Clinical and histological characterization of multifocal, spontaneous, noninfectious alopecia in Norwegian puffin dogs (lundehunds). Vet Dermatol. 2014:25:112- 119.

Frazer MM et al. Sebaceous adenitis in Havanese dogs: a retrospective study of the clinical presentation and incidence Vet Dermatol. 2011:22: 267-274.

Gross TL, Ihrke P., Walder EJ, Affolter VK: Skin diseases of the dog and cat. Clinical and histopathologic diagnosis. 2nd ed. Blackwell Science. 2005.

102

Gross, T.L. & Kunkle, G.A. The cutaneous histology of dermatomyositis in Collie dogs. Vet Pathol. 1987; 24: 11-15.

Gross, T.L. Olivry T, Tobin D. Morphologic and immunologic characterization of a canine isthmus mural folliculitis resembling pseudopelade of humans. Vet Dermatol. 2000;11:17- 24.

Hargis, A.M. & Mundell, A.C. Familial canine dermatomyositis. Comp on Cont Ed 1992; 14: 855-863

Hargis, A.M. , Prieur, D.J , Haupt, K.H. , McDonald, T.L. , Moore, M.P. Prospective study of familial canine dermatomyositis. Correlation of the severity of dermatomyositis and circulating immune complex levels. American Journal of Pathology 1986; 123: 465-479.

Lam ATH et al. ORAL VITAMIN A AS AN ADJUNCT TREATMENT FOR CANINE SEBACEOUS ADENITIS . Vet Dermatol. 2011:22: 305-311.

Lortz J, Favrot C, Mecklenburg l, Nett C, Rüfenacht S, Seewald W, Linek M. A multicentre placebo-controlled clinical trial on the efficacy of oral ciclosporin A in the treatment of canine idiopathic sebaceous adenitis in comparison with conventional topical treatment. Vet Dermatol. 2010;21:593-601.

Miller WH Jr, et al: Muller & Kirk’s Small animal dermatology 7 th ed., St. Louis, 2013, Elsevier Saunders.

Morris DO. Ischemic Dermatopathies Vet Clin Small Anim 2013; 43:99-111.

Parker, W.M. & Foster, R.A. Cutaneous vasculitis in five Jack Russell Terriers. Vet Dermatol.1996;7:109-115.

Reichler IR. et al. SEBACEOUS ADENITIS IN THE AKITA : CLINICAL OBSERVATIONS, HISTOPATHOLOGY AND HEREDITY . Vet Dermatol. 2001;12;243-253.

Vitale CB, Gross TL, Magro CM. Vaccine-induced ischemic dermatopathy in the dog. Vet Dermatol. 1999;10:131-142.

Wilcock, B.P. & Yager, J.A. Focal cutaneous vasculitis and alopecia at sites of rabies vaccination in dogs. J of the Am Vet Assoc 1986;188:1174-117 7.

103

104

ALOPECIA – X

Manon Paradis, DMV, MScV, Dipl. ACVD, Department of clinical sciences, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.

INTRODUCTION

Alopecia X is the name most veterinary dermatologists are now using to refer to the following disease(s): pseudo-Cushings, adult onset growth hormone (hyposomatotropism) deficiency, growth hormone responsive alopecia, castration-responsive alopecia, adrenal sex hormone imbalance, congenital adrenal hyperplasia like-syndrome, Lysodren responsive dermatosis, post-clipping alopecia (of plush-coated breeds), follicular dysplasia of Husky and other Nordic breeds (Woolly syndrome, coat funk in malamute), follicular growth dysfunction of the plush-coated breeds, black skin disease of Pomeranians, and more recently hair cycle arrest . The diversity in proposed names is based, at least in part, upon the differences in endocrine evaluation results and/or clinical responses to various therapeutic modalities.

AETIOPATHOGENESIS

Alopecia X is a disorder on which so much has been said and written but for which little is really known or understood. The aetiology remains obscure although a genetic predisposition to an unidentified hormonal imbalance is plausible, but a defect residing at the hair follicle level is also possible. If the problem is a primary disorder of the hair growth cycle, various stimuli (including different hormones) could draw hair follicles into anagen phase.

In the 80’s, the hypothetical pathogenesis of alopecia X was an adult onset growth- hormone deficiency. This theory was however discarded since many dogs with this condition had normal growth hormone levels.

In the 90’s, the theoretical pathomechanism was an imbalance of adrenal steroid intermediates and sex hormones, possibly due to a deficiency in 21-hydroxylase enzyme. However, it was later shown that not all dogs with alopecia X have abnormalities in adrenal steroid or sex hormone concentrations and that there was no association of hair regrowth with changes in hormone concentrations. In addition, a decrease in hormone concentrations was not necessarily observed in neutered dogs showing favourable response following melatonin administration. Moreover, the canine 21-hydroxylase gene was later cloned and sequenced in Pomeranians with alopecia X, and no mutations in the gene were detected.

It has also been suggested that the alopecia may be due to a mild but prolonged increase in basal cortisolemia, instead of adrenal sex hormone imbalance . This hypothesis was based on work done in miniature poodles and Pomeranians with alopecia X which had increased

105

urinary cortisol/creatinine ratios but normal post-ACTH stimulation cortisol levels. However, this theory seems unlikely because no other clinical signs of hypercortisolemia (pu/pd, polyphagia, pendulous abdomen, etc.) are seen in dogs with alopecia X.

It is possible that miniature Poodles (anagen based hair growth cycle) have a different aetiopathogenesis than the plush-coated breeds (telogen based hair growth cycle). Paradoxically, however, it was found in a retrospective evaluation of adrenal hormone panels that adrenal sex hormone levels in miniature Poodles most resemble Pomeranians, and both breeds often show hair regrowth following the same therapy (e.g., trilostane).

New theories on the aetiopathegenesis of alopecia X are focusing on genetics and hair follicle receptors. Extrinsic (e.g., hormones) as well as intrinsic (e.g., cytokines, growth factors, receptors) factors are involved in the hair follicle cycle. Anagen initiation involves complex interactions between factors (oestrogen receptors among others). The role of oestrogen receptors was investigated in a cohort of Pomeranians (excluding intact females) with alopecia X. Hair regrowth following melatonin administration (which may block oestrogen receptors) was not associated with a change in oestrogen receptor-α staining. It is possible that hair follicles of dogs with alopecia X require stimulation from other molecules (e.g., noggin, insulin growth factors, etc.) in conjunction with blocking of the oestrogen receptors.

There is growing evidence that androgens might be involved in this syndrome. Indeed, significant hair growth has been observed in a number of dogs with alopecia X following castration, as well as with the use of various antiandrogen drugs such as osaterone acetate, deslorelin, finasteride and dutasteride. Alopecia X, which occurs most commonly in breeds bred for hirsutism (double coat and dense under coat), may indeed be caused by a primary follicular defect, similar to male pattern baldness, with a sex-hormone related signal for expression. Indeed, men with pattern baldness do not always have elevated sex hormone concentrations; instead their hair follicles respond abnormally to a normal hormonal signal (e.g. receptor problems).

CLINICAL FEATURES

Alopecia X is seen in many breeds, but especially in Nordic breeds with plush coat (e.g., Pomeranian, Chow Chow, Keeshond, Samoyed, Malamute and Husky), and miniature poodle. The age at onset of alopecia is quite variable occurring usually between 1 to 10 years of age. Dogs of both sexes can be affected regardless of neutering status. Alopecia can start before or after neutering. Permanent hair regrowth is often observed following castration of affected intact male dogs.

The symmetrical, non-inflammatory alopecia observed in alopecia X mimics that of endocrine alopecia. Initially, there is loss of primary hairs (with retention of secondary hairs) in frictional areas (around the neck, caudo-medial thighs and tail). Gradually, all hair is lost in those regions and eventually the truncal primary hairs are also lost, giving the remaining coat a puppy-like appearance. With time (several months to years), the secondary hairs become sparse, and hyperpigmentation of the exposed skin and/or colour change in the remaining hair coat may be seen. The head and legs are usually spared. A tendency to regrow hair at the biopsy site following skin biopsy or traumatic stimuli (e.g. skin scraping,

106

sunburn, pyoderma) is a common finding (however not constant or pathognomonic) in this syndrome.

DIFFERENTIAL DIAGNSOSIS

This includes hypothyroidism, spontaneous and iatrogenic hyperadrenocorticism, hyperoestrogenism due to functional gonadal neoplasms for human oestrogen cream, telogen defluxion, other follicular dysplasias, and, in some cases, sebaceous adenitis.

DIAGNOSIS

The diagnosis is based on history, physical examination findings and by exclusion of disorders listed in differential diagnosis.

Histopathological examination of skin biopsies reveals changes consistent with endocrinopathies. Decreased amount and size of dermal elastin fibers were reported (chronic cases) in initial reports of “adult onset growth hormone deficiencies”. Later, the presence of "flame follicles" (excessive tricholemmal keratinisation) gained popularity over the elastin fibers. It is not known whether the flame follicle is simply a nonspecific expression of follicular growth arrest in the plush-coated breeds, or whether haircoat abnormalities featuring flame follicles are united by a common aetiopathogenesis. However, even if flame follicles are neither pathognomonic nor observed in every cases of alopecia X, histopathological evaluation should at least confirm atrophic/endocrine changes and rule out other disorders such as sebaceous adenitis or colour-linked follicular dysplasia.

Results of routine laboratory tests (CBC, chemistry profile, urinalysis) are typically normal, as are those for thyroid and adrenal function tests. Reproductive hormone panel (measured before and following ACTH stimulation) has been recommended in the past. However, a retrospective study has demonstrated its uselessness in ruling in or ruling out alopecia X.

TREATMENT

In an intact male, the first recommendation is castration . More than 50% of the dogs will regrow a normal hair coat which is generally permanent. Although less frequently documented in intact female dogs, this syndrome may also respond to ovariohysterectomy.

In neutered animals, numerous forms of therapy have been associated with hair regrowth but unfortunately the result is not predictable and may be a short-term effect.

Oral melatonin is currently the most popular first line of treatment. It is cheap and safe, and partial to complete hair regrowth occurs in approximately 30 to 40% of the cases when administered at the rate of 3-6 mg/dog q8 to 12h for 3 to 4 months. The exact mechanism by which melatonin induces hair growth in alopecia X is not known. The hair growth might be due to either modulation of sex hormone levels, interference with cortisol production, action at the hair follicle level by blocking oestrogen receptors (oestrogen can inhibit anagen initiation) or a less likely actual melatonin deficiency.

107

Mitotane (Lysodren ®, O,p'-DDD) has been reported to be efficacious in dogs with alopecia X. Although the induction dose recommended is lower than for hyperadrenocorticism (e.g., 15-25 mg/kg, q24h for 5 days, then q7-14 days as maintenance), the side effects such as hypoadrenocorticism associated with this drug should be carefully considered before using it in affected animals, and close monitoring is essential.

Trilostane (Vetoryl ®), a competitive inhibitor of β-hydroxysteroid dehydrogenase, which interferes with adrenal steroidogenesis, has been used with success in many Pomeranians, miniature Poodles, and malamutes with alopecia X. The main disadvantages of this treatment modality is its cost and the possibility (albeit uncommon) of adrenal necrosis.

Medroxyprogesterone acetate was investigated in a recent study because it is known that synthetic progestins can induce growth hormone secretion in the mammary gland of dogs. Following four monthly subcutaneous injections, partial hair regrowth was observed only in a few dogs. Although no side effects were observed in this study, prolonged administration of medroxyprogesterone acetate may induce mammary nodules, cystic endometrial hyperplasia, and diabetes mellitus.

A growing body of evidence suggests that androgens are involved in alopecia X. In addition to the hair regrowth observed in a large number of intact male dogs suffering alopecia X following castration, success has also been obtained with various anti-androgen drugs such as osaterone acetate, deslorelin, finasteride and dutasteride.

Osaterone acetate (Ypozane ®) is a steroid with potent anti-androgen and partial progestagen effect, licensed for the treatment of canine benign prostatic hyperplasia. Success rate of up to 75% has been obtained with this drug when administered daily orally for one week every 3 months (Vetderm Listserv survey).

Recently, Deslorelin (Suprelorin ®), a long acting GnRH agonist commercialized as implants for reversible chemical castration in dog, was shown effective in the majority of intact male dogs, but was generally ineffective in spayed females affected with alopecia X.

5-α-reductase inhibitors such as finasteride and dutasteride block the action of the 5-α- reductase enzyme that converts testosterone to dihydrotestosterone. Finasteride (a type II 5-α-reductase inhibitor) significantly decreases serum and tissue dihydrotestosterone concentrations in humans and in dogs.

In men with androgenic alopecia, the balding scalp with its miniaturized follicles contains increased amounts of dihydrotestosterone compared with the nonbalding scalp. Oral administration of finasteride (Propecia ® 1 mg/tablet) daily decreases scalp and serum dihydrotestosterone concentrations, and promotes hair growth although continued daily use of finasteride is needed in man for sustained benefit.

Finasteride (Proscar ®, 5 mg/tablet) has been used in the treatment of benign prostatic hyperplasia in man and in dogs and appears to be safe. Dutasteride (Avodart ®, 0.5 mg/capsule), a dual (type I and II) 5-α-reductase inhibitor, is also approved for the treatment of benign prostatic hyperplasia in man. Although not labelled for androgenic alopecia in men, it very effectively promotes hair regrowth. Both of these drugs we effective in a few dogs with alopecia X treated by the author. Current studies are investigating the presence of type I and type II 5-α-reductase enzyme in the dog skin.

108

Other treatment modalities such as exogenous oestrogen, methyltestosterone, growth hormone, leuprolide acetate, L-deprenyl, and medroxyprogesterone acetate have been recommended or investigated. However, these therapies are no longer recommended due to adverse effects, cost, availability and / or poor effectiveness.

PROGNOSIS

Alopecia X is essentially an aesthetic problem. With the exception of a few dogs where a superficial pyoderma will be seen, these dogs are otherwise healthy.

If melatonin is not helpful, the pros and cons of the various therapeutic options need to be discussed with the owner. It is important to state that benign neglect is considered a valid management alternative. Due to cost, availability and/or side effects related to various treatments, owners will often choose not to have their dogs treated. Rather than promoting more aggressive treatments (e.g. mitotane, trilostane), one’s efforts could be toward client education and promotion of acceptance of the alopecia (i.e. “sweater therapy”).

REFERENCES

Albanese F, Malerba E, Abramo F, Miragliotta V, Fracassi F. Deslorelin for the treatment of hair cycle arrest in intact male dogs. Vet Dermatol. 2014;25:

Behrend EN, Kennis R. Atypical Cushing’s syndrome in dogs: Argument for and against. Vet Clin Small Anim. 2010;40:285-296.

Cerundolo R. Lloyd DH. Persechino A. Evans H. Cauvin A. Treatment of canine Alopecia X with trilostane. Vet Dermatol. 2004; 15:285-293.

Cerundolo R. Lloyd DH.Vaessen MMAR. Mol JA. Kooistra HS. Rijnberk A. Alopecia in pomeranians and miniature poodles in association with high urinary corticoid:creatinine ratios and resistance to glucocorticoid feedback. VetRec. 2007; 160:393-397.

Cerundolo R, Warren S. The use of deslorelin to promote hair regrowth in dogs with Alopecia X. Annual congress of ESVD/ECVD 2013.

Eigenmann JE, Patterson DF. Growth hormone deficiency in the mature dog. J Am Anim Hosp Assoc 1984;20:741-746.

Frank LA Growth hormone responsive alopecia in dogs. J Am Vet Med Assoc. 2005;226:1494-1947.

Frank LA, Hnlica KA, Oliver JW. Adrenal steroid hormone concentrations in dogs with hair cycle arrest (Alopecia X) before and during treatment with melatonin and mitotane. Vet Dermatol. 2004;15:278-284.

109

Frank LA, Schmeitzel LP and Oliver JW. Steroidogenic response of adrenal tissues after administration of ACTH to dogs with hypercortisolemia. J Am Vet Med Assoc 2001;218: 214-216.

Frank LA, Hnilica KA, Bohrbach, B, Oliver JW. Retrospective evaluation of sex hormones and steroid hormone intermediates in dogs with alopecia. Vet Dermatol. 2003;14:91-97.

Frank LA, Donnell RL, Kania SA. Oestrogen receptor evaluation in Pomeranian dogs with hair cycle arrest (Alopecia X) on melatonin supplementation. Vet Dermatol. 2006;17:252- 258.

Frank LA. Oestrogen receptor antagonist and hair regrowth in dogs with hair cycle arrest (Alopecia X). VetDermatol. 2007;18:63-66.

Frank LA, Watson JB. Treatment of alopecia X with medroxyprogesterone acetate. Vet dermatol. 2013;24:624-627.

Gross TL, Ihrke P., Walder EJ, Affolter VK: Skin diseases of the dog and cat. Clinical and histopathologic diagnosis. 2nd ed. Blackwell Science. 2005.

Gross TL. The sex hormone/growth hormone dermatoses: the view of a pathologist. Proc Thrird World Congr Vet Dermatol Edinburgh 1996 pp.79-81.

Huang HP, Lien YH, Chang PH. Effect of castration on hair regrowth in Pomeranians with hair cycle arrest (Alopecia X) J Vet Clin Sc, 2009; 2: 17-19.

Kamolpatana K, Johnston SD, Hardy SK (1998) Effect of finasteride on serum concentrations of dihydrotestosterone and testosterone in three clinically normal sexually intact adult male dogs. Am J Vet Res 58: 762-764.

Leone F, Cerundolo R, Vercelli A et al. The use of trilostane for te treatment of alopecia X in Alaskan malamutes. J Am Anim Hosp Assoc. 2005;41:336-342.

Lothrop CD. Pathophysiology of canine growth hormone-responsive alopecia. Comp Cont Educ Pract Vet 1988;10: 1346-1349.

Mausberg EM, Drögmüller C, Dolf G, Rüfenacht S,Welle M, Leeb T. Exclusion of patched homolog 2 (PTCH2) as a candidate gene for alopecia X in Pomeranians ans Keeshonden. Vet Rec. 2008;163:121-123.

Miller WH, Griffin CE, Campbell K. Hair cycle arrest In: Muller & Kirk’s Small animal dermatology 7th ed Saunders WB, Philadelphia, 2013. pp. 537-540.

Paradis M. Melatonin therapy in canine alopecia. Bonadura ED. In Kirk’s Current Veterinary Therapy XIII. WB Saunders Philadelphia. 1999, pp 546-549.

Paradis M, Cerundolo R. Genodermatosis : alopecia and hypotrichoses. Advance in Veterinary Dermatology Vol 5. Blackwell publishing. 2005, pp.360-364.

110

Paradis M. Melatonin-responsive alopecia in dogs. 15 th Proceedings of AAVD/ACVD Meeting, Maui, Hawaii. 1999. Pp. 123-130.

Paradis M. Alopecia X. Derm Dialogue. Summer 2002 pp.12-14.

Paradis M. Alopecia X. Clinical Veterinary Advisor Dogs and Cats. 3rd ed. E. Coté ed. Mosby Elsevier. 2015 pp. 51-52.

Paradis M. Alopécie-X. Indispensables de dermatologie 2è édition. Med’Com ed. 2009 pp. 225-229.

Parker WM and Scott DW. Growth hormone responsive alopecia in the mature dog: A discussion of 13 cases. J Am Hosp Anim Assoc 1980;16: 824-828.

Post K, Dignean MA and Clark EG. Hair follicle dysplasia in a Siberian Husky. J Am Anim Hosp Assoc. 1988;24:659-662.

Rest JR, Lloyd DH, Cerundolo R. Histopathology of alopecia X. Vet Dermatol. 2004;15: 23.

Rosenkrantz WS and Griffin CE. Lysodren therapy in suspect adrenal sex hormone dermatosis. Proc World Cong Vet Dermatol. 1992;2:121.

Rosenkrantz WS. The sex hormone/growth hormone dermatoses: the view of the clinician. Proc Thrird World Congr Vet Dermatol. Edinburgh 1996 pp.75-78.

Rosser EJ. Sex-hormones. In: Griffin CE, Kwochka KW, MacDonald JM eds. Current Veterinary Dermatology: the science and art of therapy. Saint Louis, Mosby 1993; pp.288- 291.

Rosser EJ. Castration-responsive dermatosis in the dog. In Von Tscharner C, Halliwell REW, eds. Advances in Veterinary dermatology. London, Baillière Tindall 1990; pp.34-42.

Shanley KJ, Miller WH. Adult onset growth hormone deficiency in siblings Airedale terriers. Comp Continuing Educ Pract Vet 1987; 9:1076-1082.

Shibata K, Koie H, Nagata M. Congenital adrenal hyperplasia-like syndrome in 51 pomeranians: a comparison with adrogenetic alopecia in humans. Proceedings of the 16 th annual AAVD/ACVD meeting. 2001 April 4-8, Norfolk. p.18.

Schmietzel LP and Lowthrop CD. Hormonal abnormalities in Pomeranians with growth hormone-responsive dermatosis. J Am Vet Med Assoc 1990;197: 1333-1341.

Schmietzel LP, Lowthrop CD and Rosenkrantz WS. Congenital adrenal-hyperplasia-like syndrome. In Bonadura. JD (ed) Kirk's Current Veterinary Therapy XII. WB Saunders Co. Philadelphia. 1995 pp.600-604.

111

Schmietzel LP. Sex hormone-related and growth hormone related alopecias. Vet Clin North Am Small Anim Pract. 1990;20:1579-1601.

Schmietzel LP Alopecia X of Nordic Breeds. 15 th Proceedings of AAVD/ACVD Meeting, Maui, Hawaii. 1999 pp. 131-138.

Scott DW and Walton DK. Hyposomatotropism in the mature dog: a discussion of 22 cases. J Am Anim Hosp Assoc 1986; 22:467-473.

Song TY, Lien YH, Chang PH, Huang HP. Effect of castration on hair regrowth in Pomeranians with hair cycle arrest (Alopecia X). 2008 Abstract WCVD6, Hong Kong.

Takada K, Kitamura H, Tikiguchi et al. Cloning of canine 21-hydroxylase gene and its polymorphic analysis as acandidate gene for congenital adrenal hyperplasia-like syndrome in Pomeranians. Res Vet Sci 2002; 73:159-163.

112

INFECTIOUS CAUSES OF ALOPECIA

Manon Paradis, DMV, MScV, Dipl. ACVD, Department of clinical sciences, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.

INTRODUCTION

Skin infection (e.g., bacterial folliculitis, Malassezia dermatitis, dermatophytosis, demodicosis) are frequent causes of focal or multifocal alopecia. The hair loss usually results from the inflammation and direct damage to the hair follicles. In addition, in pruritic disorders, self-inflicted alopecia often aggravates the hair loss caused by the infection itself.

The aim of this presentation is to overview the clinical features and diagnosis of the infectious causes of alopecia.

BACTERIAL INFECTION

Bacterial pyoderma is common in dogs and most cases are caused by coagulase-positive Staphylococcus pseudintermedius , a normal component of canine skin flora.

CLASSIFICATION

Pyoderma can be subdivided in (1) surface pyoderma (infection restricted to the surface layer of the epidermis) which includes intertrigo (skin fold pyoderma), acute moist dermatitis (pyotraumatic dermatitis, hot spots), and bacterial overgrowth syndrome (BOGS); (2) superficial pyoderma (infection involving the epidermis and the infundibular portion of the hair follicle) which includes impetigo, superficial bacterial folliculitis (SBF), exfoliative superficial pyoderma (superficial spreading pyoderma), and mucocutaneous pyoderma, and; (3) deep pyoderma (bacterial infection extending beyond the hair follicle to involve the dermis and subcutis, which may lead to cellulitis) which include acne, pyotraumatic furunculosis, nasal folliculitis and furunculosis, interdigital furunculosis/ pododermatitis, infected acral lick dermatitis, callus pyoderma, postgrooming furunculosis, and German shepherd pyoderma.

UNDERLYING AETIOLOGIES

Some types of pyoderma, particularly SBF and BOGS are often secondary to underlying aetiologies such as allergic skin diseases (atopic dermatitis, cutaneous adverse food hypersensitivity, flea bite hypersensitivity), endocrinopathies (e.g., hypothyroidism, hyperadrenocorticism), parasitic skin disease (e.g., Sarcoptes , Demodex spp.), immune-

113

mediated diseases, cornification disorders (e.g., sebaceous adenitis) and follicular dysplasia (e.g., colour dilution alopecia). Deep pyoderma may be associated with demodicosis and other underlying immuno-incompetence. Any therapeutic plan for controlling pyoderma without considering underlying predisposing factors is destined to fail.

CLINICAL FEATURES

In SBF, one can observe papules, pustules, epidermal collarettes, and patchy alopecia producing a “moth-eaten” appearance of the haircoat over the trunk. Resolving lesions may show central hyperpigmentation (“bull’s-eye” lesion). In exfoliative superficial pyoderma, large epidermal collarettes with an erythematous leading edge is seen over the trunk. The associated exudate may form crusts.

Level of pruritus can be quite variable in superficial pyoderma, varying from absent to severe. In addition to the alopecia resulting from the inflammatory process, a variable level of alopecia may result from self-trauma due to pruritus.

DIAGNOSIS

The dermatological examination alone may provide a strong suspicion of pyoderma. Epidermal collarettes are extremely useful secondary skin lesions to look for (clip some hair if needed); they are strongly suggestive of a superficial pyoderma. Presence of a haemorrhagic discharge, resulting from a breach in the basal membrane, is evocative of a deeper bacterial infection (furunculosis).

Skin cytology is very useful to confirm the infection (e.g., degenerated neutrophils, free and phagocytized cocci). Bacterial culture and sensitivity may be required, particularly if there has been a failure to respond to rational antibiotic therapy or if bacilli are noted on skin cytological examination.

DIFFERENTIAL DIAGNOSIS

Dermatophytosis and demodicosis have a similar clinical presentation. Pemphigus foliaceus and epitheliotrophic lymphoma may also present as pyodermas that fail to respond to appropriate antibiotic therapy. In these instances, skin biopsy is indicated to confirm the diagnosis.

TREATMENT

Treatment usually consists of oral antibiotic (for a minimum of 3 weeks and for 1-2 weeks beyond clinical cure) accompanied with topical antiseptic treatment (e.g., chlorexidine) more commonly in the form of shampoo.

114

FUNGAL INFECTION

Yeast ( Malassezia) dermatitis and dermatophytosis, two superficial fungal skin infections, are relatively common cause of alopecia in dogs.

YEAST ( MALASSEZIA ) DERMATITIS

Yeast dermatitis is a common pruritic dermatitis caused by the overgrowth of Malassezia spp. yeast on skin surface.

AETIOLOGY

Most infections are caused by the lipophilic unicellular organism Malassezia pachydermatis , which is part of the normal skin microflora. The yeast can become opportunistic invaders when changes occur in the cutaneous microclimate (e.g., lipid composition, relative humidity) or defense mechanisms (e.g., immunosuppression, epidermal barrier dysfunction). Once colonization takes place, yeasts release proteases and lipases that alter cutaneous homeostasis, allowing for continued yeast overgrowth. In addition, in some atopic dogs with cytologic demonstration of yeasts, Malassezia may elicit a type-I cutaneous hypersensitivity reaction.

Specific disorders that predispose to cutaneous Malassezia overgrowth include allergic skin disease (e.g., atopic dermatitis, adverse cutaneous adverse reaction, flea bite hypersensitivity, contact allergy), endocrinopathies (e.g., iatrogenic or spontaneous hyperadrenocorticism, hypothyroidism, hyperthyroidism, diabetes mellitus), cornification disorders, nutritional deficiencies and metabolic diseases (e.g., superficial necrolytic dermatitis, zinc-responsive dermatosis).

CLINICAL FEATURES

Moderate to intense pruritus is the most common complaint but rancid offensive odour, oily coat, alopecia, erythroderma, lichenification and scaling are frequently observed. Skin lesions reflect existing pruritus and are not specific to Malassezia dermatitis.

Localized yeast dermatitis involves the face (perioral, muzzle, ears), ventral aspect of the trunk (neck, axillae, inguinal area), ventral tail and perianal area, skin folds, or paws (interdigital web and nail fold).

Generalized yeast dermatitis involves several regions as described above. Lesional skin may be erythematous, scaly, greasy or dry, alopecic, saliva-stained, and excoriated. Hyperpigmented lichenification is seen in more chronic lesions. A brown waxy discharge may be observed in the claw folds with extension onto the claws proper.

115

DIAGNOSIS

Skin cytology is the most reliable diagnostic procedure and should be performed on every dog with compatible historical and physical findings. Skin scrapings are also indicated to exclude ectoparasites.

DIFFERENTIAL DIAGNOSIS

The differential diagnosis includes most pruritic skin diseases encountered in dogs, particularly superficial pyoderma, allergic skin disease and sarcoptic mange.

TREATMENT

Treatment consists of keratomodulating and antiyeast topical treatment and systemic antifungal treatment such as ketoconazole (5-10 mg/kg PO q24h with food). It is important to look for and treat the underlying predisposing diseases.

DERMATOPHYTOSIS

Dermatophytosis is a superficial fungal skin disease of hair, skin or claws.

AETIOLOGY

In order of prevalence, causative fungal species include Microsporum canis , Microsporum gypseum , and the Trichophyton group. Dermatophytes are not part of the normal fungal flora. Dermatophytosis is a self-curing disease in healthy animals and most infections will resolve without treatment in 1 to 3 months. Recovery is typically associated with development of a strong cell mediated immunity.

CLINICAL FEATURES

Lesions are characterized by focal to multifocal areas of alopecia, scaling, crusting, with or without erythema, and variable pruritus.

DIAGNOSIS

Diagnosis is based on a combination of compatible clinical signs and confirmation of infection of the lesions. Active infections are documented by Wood’s lamp, microscopic examination of infected hairs and fungal culture. M. canis is the only veterinary pathogen that fluoresces (in approximately 50% of the cases) when exposed to UV light. Positive fluorescence is apple green and found only on the hair shaft (never nails or crusts). Wood’s lamp positive hairs can be plucked and mounted in mineral oil for direct

116

microscopic examination or used for fungal culture. All suspect colonies must be microscopically confirmed, using methylene blue or lactophenol cotton blue stain.

DIFFERENTIAL DIAGNOSIS

Superficial pyoderma and demodicosis have similar a clinical presentation and are more common in dogs; therefore, these disorders should be suspected first.

TREATMENT

Treatment consists of antiyeast topical treatment such as enilconazole or lime sulfur dips, and systemic antifungal treatment such as ketoconazole (5-10 mg/kg PO q24h with food).

PARASITIC INFESTATIONS

Various ectoparasitic infestations can cause alopecia by their direct damage to the hair follicle (demodicosis) or from self-trauma due to the intense pruritus (sarcoptic mange and flea bite hypersensitivity).

DEMODICOSIS

Demodicosis is a common alopecic disease in dogs.

AETIOLOGY

Skin lesions develop secondary to overgrowth of Demodex canis mites in the hair follicles.

CLINICAL FEATURES

Canine demodicosis is classified as localized or generalized demodicosis. Localized demodicosis is most common in young dogs between 3 to 8 months of age. Lesions, consisting of one or more localized areas of alopecia, erythema, and scaling, are typically found on the face and forelimbs.

Canine generalized demodicosis may be classified as juvenile onset (affecting dogs from 3 to 18 months of age) or adult onset (affecting middle-aged to older dogs, often immunocompromised animals with underlying hyperadrenocorticism, hypothyroidism, diabetes mellitus, immunosuppressive drug therapy, or neoplasia). Clinical signs are variable and may start with localized lesions that spread. Secondary deep bacterial infection (furunculosis) is very common.

117

DIAGNOSIS

Diagnosis is confirmed with deep skin scrapings or hair plucks (trichoscopy) revealing numerous adult D. canis mites and its immature forms (nymph, larvae and ova). General health of the dog should be evaluated, particularly in the adult-onset form, and any underlying diseases or concurrent infections should be treated.

OTHER PARASITIC INFESTATIONS

Flea bite allergy dermatitis and sarcoptic mange (canine scabies) can result in significant amount of alopecia. However, pruritus, is usually the initial and most important clinical sign.

In sarcoptic mange, the mites often affect the ear pinnae margins and elbows. Female mites burrow through the epidermis and lay their eggs in the resulting tunnel. Many dogs develop a hypersensitivity reaction to mite antigens. Clinical features include an intensely pruritic, nonseasonal dermatitis with papules, excoriations, thick yellowish crusts, and alopecia. Lesions may rapidly generalize, but the dorsum is usually spared.

In flea bite hypersensitivity, pruritus and lesions (papules, crusts, excoriations, erythema, and alopecia) typically develop over the dorsal lumbosacral region, tail head, and caudomedial thighs.

REFERENCES

Hannigan M. Canine pyoderma. In Coté E, editor: Clinical Veterinary Advisor 3 rd ed. 2015. pp 874-876.

Hillier A et al. Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis (Antimicrobial guidelines Working group of the international society for companion animal infectious diseases). Vet Dermatol. 2014;25:163-175.

Miller WH Jr, Griffin CE, Campbell KL. Muller & Kirk’s Small animal dermatology 7 th ed. Elsevier Saunders.St. Louis, 2013.

Moriello K. Dermatophytosis. In Coté E, editor: Clinical Veterinary Advisor 3rd ed. 2015. pp 266-269.

Mueller RS, Bensignor E, Ferrer L, Holm B, Lemarie S, Paradis M, Sphipsone MA. Treatment of Demodicosis in Dogs: a Clinical Practice Guidelines. Vet Dermatol. 2012;23:86-96.

Noli C, Morris DO. Staphyloccocal pyoderma. In Jackson H, Marsella R, editors: BSAVA Manual of canine and feline dermatology, 3 rd ed., Gloucester, UK, BSAVA. 2012. pp 173- 187. Rees C: An approach to canine focal and multifocal alopecia. In Jackson H, Marsella R, editors: BSAVA Manual of canine and feline dermatology 3 rd ed., Gloucester, UK, BSAVA. 2012. pp 86–90.

118

ASE ISCUSSIONS C D

Manon Paradis, DMV, MScV, Dipl. ACVD, Department of clinical sciences, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Québec, Canada.

FREUD

Pyrenean mountain dog X Collie Intact male dog 9 year old 28 kg 3 year history of alopecia

NOTES:

119

CHI CHI

Chihuahua Neutered male dog 9 year old 3 kg Skin issue progressing for 4 months

NOTES:

120

JULES

Newfoundland Neutered male dog 8 year old 62 kg Skin issue progressing for 1.5 years

NOTES:

121

122

EQUINE CUSHINGS DISEASE

Richard Morris BSc BVetMed CertVD MRCVS Advice and Support: Dr Neil McEwan BVM&S, MVM, DVD, DipECVD, DVM, MRCVS

Richard Morris gained a BSc in Immunology and Pharmacology from King’s College London in 1987, qualified as a vet from the Royal Veterinary College in 1990 and has worked in farm, equine and small animal practice in the UK and New Zealand. He passed the Certificate in Veterinary Dermatology in 1996 and runs a dermatology clinic in The Fenwold Veterinary Practice in Lincolnshire where he is a partner.

AIMS & OBJECTIVES

The aims and objectives of this study were to review the incidence of presenting signs in a group of 30 horses seen in general practice with suspected Equine Cushings Disease over a period of two years and review how these may differ from previous descriptions of ECD.

INTRODUCTION AND BACKGROUND

Equine Cushings Disease (ECD) is the most commonly encountered equine endocrine disorder 1 producing a range of symptoms that include; excessively long coat (hirsutism) 2, excessive sweating, secondary bacterial cutaneous infections, parasitism, oral ulceration and dental disease 3, recurrent bouts of laminitis, polydipsia and polyuria, lethargy, bulging of the supra orbital fat pad, muscle wastage and a pendulous abdomen 4 (see fig 1-4). In recent years increased owner awareness and improved diagnostics have led to a decrease in the number of cases presenting with these classic signs.

123

THERE ARE TWO FORMS OF EQUINE CUSHINGS DISEASE 5:

1. PARS PITUITARY INTERMEDIA DISEASE (PPID)

Typically, dopamine from the hypothalamus inhibits production of ACTH from the Pars Intermedia of the pituitary; in older horses, reduced production of dopamine due to ageing, allows uncontrolled proliferation of the Pars Intermedia and excessive production of pro- opiomelanocortin (POMC) derived peptides (including ACTH, alpha melanocyte stimulating hormone, beta-endorphin and corticotrophin-like intermediate peptide (CLIP), which stimulates the pancreas to secrete increased levels of insulin. PPID is seen more commonly in older horses (over 15 years old).

2. EQUINE METABOLIC SYNDROME (EMS) (PERIPHERAL CUSHINGS DISEASE)

Insulin resistance (IR) develops due to excess deposition of fat and reduced activity (similar to type II diabetes in people), seen more commonly in younger horses and ponies (4-15 years old).

Both conditions result in insulin dysregulation 6 affecting the health and well-being of the affected individual.

Diagnosis is based on the presenting clinical signs and confirmed with blood tests. For PPID elevated resting ACTH levels are helpful (specificity 97%, sensitivity 84%) 7 and can be carried out at most commercial labs. The resting levels are affected by day length; cut- off point has been established as <35 pg/ml from November to June, and <45pg/ml from July to October, suggesting autumn is a good time to test 7.

EMS can be diagnosed by measuring resting insulin levels after a 6 hour fasting period – levels exceeding 65 ulU/ml were used at Cambridge Specialist Lab. (CSL) to indicate IR, the specificity is high but the sensitivity is low. Dynamic testing using a combined glucose- insulin tolerance test (in-feed glucose test) can be used to confirm the diagnosis but requires overnight fasting and two blood samples 5 which is not practical for many cases in general practice.

Treatment of ECD includes management changes and medical therapy. Management changes include diet control- feeding a high fibre diet (soaking hay for 14 hours reduces the calorific content), putting on a muzzle, strip grazing pasture, and increasing the amount of exercise. A range of medical treatments have been tried including Metformine 8 and Pergolide (starting dose 0.002mg/kg). Currently, only Pergolide is licensed to treat equidae under the trade name Prascend (Boehringer).

MATERIALS AND METHODS

Blood samples from 30 horses and ponies presented with clinical signs that were consistent with ECD were collected and put into diagnostic categories of PPID, EMS or no evidence of ECD. For financial reasons in many cases only an initial resting ACTH test was performed and if PPID not diagnosed a further laminitis profile test which included insulin

124

levels was carried out to check for EMS. Laboratory samples for ACTH testing were taken in EDTA tubes, the plasma separated and then sent in a plain tube in a chiller pack. A diagnosis of PPID was made if ACTH levels were over 35pg/ml on samples taken between November and June and over 45 pg/ml July to October7. Where possible follow up blood samples were taken 4-6 weeks later to monitor the response and adjust the dose of treatment.

Insulin levels were tested on serum using radioimmuno assay at CSL and a diagnosis of EMS was made if insulin levels were over 65 uLU/ml.

RESULTS (see Table 1)

Of the 30 horses studied, 5 had no evidence of ECD on blood results, 18 were diagnosed with PPID and 7 with EMS. Laminitis was the most common presenting sign; 61% (11/18) of the PPID cases and 57% (4/7) of the EMS cases were laminitic. The other main symptom in ECD cases in this study was mental dullness and lethargy; 39% (7/18) of the PPID cases and 43% (3/7) of the EMS cases were displaying these symptoms.

Only cases 2, 12 and 18 showed the classic hirsute coat, this may be because coat clipping is now popular which masks this clinical sign. Excessive thirst and urination were only seen in cases 2, 17 and 18, secondary bacterial cutaneous infections were only seen in cases 19, 23 and 25, and dental disease was only seen in cases 13 and 14. The other symptoms of excessive sweating, bulging of the supra orbital fat pad, pot belly, and parasitism were not noted in any of the cases in this study.

CONCLUSION

From this study the most common clinical signs of ECD seen were laminitis, mental dullness and lethargy. The classic dermatological sign of hirsutism; excessive sweating, thirst and urination were not very common. This suggests that as a result of regular coat clipping by owners and increased awareness of the signs of ECD, cases are being diagnosed before the classic symptoms are apparent and as new treatments become licensed the veterinary profession is able to improve the welfare for the horse population reducing the incidence of this crippling disease.

Figure 1 - Recurrent Laminitis

125

Figure 2 - Hirsutism

Figure 3 - Sweaty Coat

Figure 4 - Bulging of the Supra Orbital Fat Pad

126

Table 1 Case Animal Age Sex Breed Main presenting Date ACTH Insulin Cortisol Glucose Treatment Outcome No (Years) symptom pg/ml 8.9-65 25-155 3.4-5.9 mIU/ml nmol/l mmol/l PPID 1 Caramel Appleyard 18 M Arab Laminitis Sep-13 106 23 418 4.4 Pergolide Improved 2 Donald Wagstaff 20 G I Draft laminitis, Aug-12 124 300 279 5.3 Pergolide Euthanasia Hirsute, pd/pu Sep-13 68 300 321 6.7 Feb-13 11.6 300 208 4.8 Aug-13 >600 11.6 132 7 3 Vinnie Dewberry 15 G Dales Cob Laminitis Sep-12 254 300 Pergolide Improved Jun-13 28 300 193 5.6 Aug-13 50 123 158 2.2 Oct-13 25 300 136 3.1 Dec-13 21 300 140 4.7 Apr-14 17 194 221 4.9 4 Troy Lovelock 16 G TBX Laminitis Jan-14 39.4 194 186 5.6 Management Euthanasia 5 Ginny Smithson 17 M Draft Laminitis Apr-14 111 173 672 4.1 Management Improved 6 Tia Maria Yates 22 M Draft Laminitis Mar-14 175 125 340 3.7 Management 7 Benji Waagensen 15 G Welsh Laminiis Aug-13 129 31 296 3 Management Improved 8 Rosie Mussett 20 M Welsh Laminitis Jul-14 76 Management 9 Murphy Castledyke 15 G Cob Laminitis Jul-14 42.5 Management 10 Rosie Adams 15 F TBX laminitis Dec-13 83 62 224 5 Management Improved 11 Bobby Hole 16 G TBX Foot Abscess/ Jan-14 60 79 122 Laminitis 12 Bill Booth 25 G TBX Dull Lethargic May-13 600 41 93 7.4 Pergolide Improved Hirsute Jun-13 91 12.8 65 3.3 Aug-13 600 11.6 132 7 13 George Mussett 34 G Welsh Dull Lethargic Jul-14 334 Management Dental Infection 14 Trooper Makepiece 20 G TBX Dull Lethargic Jul-14 87.4 Pergolide Improved Dental Infection 15 Bonnie Spencer 25 M Welsh X Dull lethargic Sep-12 140 Pergolide Improved Mar-13 44.1 Sep-13 51 16 Geofrey Haggerty 24 G Welsh Dull lethargic Oct-13 133 Management Euthanasia 17 Apollo Oscroft 29 G Cob Dull Lethargic Jun-14 72.3 Management pd/pu 18 Charm Jennings M Cob Dull Lethargic Jan-13 600 Pergolide Improved pd/pu Hirsute EMS 19 Poe Garbut 15 M Welsh Laminitis, May-13 16.7 194 113 4.5 Management Improved Dermatitis 20 Dinky Dunn 5 G Shetland Laminitis Jan-13 10 300 218 5.3 Pergolide Euthanasia 21 Danny Metson 10 G Dales Laminitis Feb-13 51 300 246 6.9 Pergolide Improved Mar-13 17.6 185 131 5.2 22 Frank L'Oest-Brown 7 G Shetland Laminitis Jun-14 23.7 58.4 2.5 Management Improved 23 Megan Jackson 16 M Welsh x TB Dermatitis/ Apr-14 25 93 183 6.3 Pergolide Improved Lethargic 24 Red Star Yates 20 G TBX lethargy Mar-14 29 177 239 11.3 Management Improved 25 Topsy Roberts 11 F Welsh Dermatitis Mar-14 15.3 >300 193 Metformine improved + Antibiotics Non Cushings 26 Eric Haggerty 15 G Shetland laminitis May-13 19.7 12.2 163 6.7 Management Improved 27 Framk Morris 7 G Shetland laminitis Jul-14 23.7 58.4 129 2.5 Management Improved 28 Rosie Banbury M Draft laminitis Apr-13 17.7 38 251 5.3 Management Improved 29 Bailey Cooper 9 G TBX laminitis May-14 6.3 28 189 4.7 Management Improved 30 Bess Chapman 6 M Shetland Laminitis Jun-14 22.7 15.5 2.1 Management Improved

127

ACKNOWLEDGEMENTS

The author would like to thank Boehringer Ingleheim for subsidising laboratory fees for the investigation of ECD with their “Talk About Laminitis” programme.

REFERENCES

1. Frank N and Geor R, Current best practice in clinical management of equine endocrine patients. Equine Veterinary Education, 2014. 26 (1): 6-9

2. Lloyd DH, Littlewood J D, Craig J M, and Thomsett L R, Practical Equine Dermatology. Pub. Blackwell Science 2003. 105-108

3. Pascoe R R R and Knottenbelt D C, Manual of Equine Dermatology. Pub W.B. Saunders 1999, 269-272

4. McGowan TW Pinchbeck GP and McGowan CM, Prevalence, risk factors and clinical signs predictive for equine pituitary pars intermedia dysfunction in aged horses. Equine Veterinary Journal 2013, 45: 74–79

5. Tadros E M and Frank N, Endocrine disorders and laminitis. Equine Veterinary Education 2013. 25 (3) 152-162

6. Marr CM and Mair TS, EVE and EVJ online collection of equine endocrinology: Recent and future directions; a great start but still a long way to go. Equine Veterinary Education 2014. 26 (1): 4-5

7. Copas VEN and Durham AE, Circannual variation in plasma adrenocorticotropic hormone concentrations in the UK in normal horses and ponies, and those with pituitary pars intermedia dysfunction. Equine Veterinary Journal, 2012. 44: 440–443

8. Rendle DI, Rutledge F, Hughes KJ, Heller K, and Durham EA, Effects of metformin hydrochloride on blood glucose and insulin responses to oral dextrose in horses Equine Veterinary Journal 2013,45 : 751–754

128

129