Veterinary Dermatology: Unusual Complaints and Case Studies

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Veterinary dermatology: unusual complaints and case studies

Author : Ariane Neuber

Categories : Clinical, RVNs

Date : December 7, 2015

Dermatology cases are frequently seen in small animal practice, making up about 20% of patients seen for appointments.

Figure 1. An indolent ulcer on the upper lip.

Skin patients often suffer from lifelong diseases and need to be managed rather than being cured. They are also a common reason for people to change practice.

Veterinary nurses can play an important part in improving the owner’s experience, gaining a successful outcome for the patient and compliance.

Flea allergy in cats

Although flea allergy is a common disease in cats, there can be slight variations to the theme,

1 / 7 making diagnosis a bit harder.

The most commonly seen clinical signs in a cat with flea allergic dermatitis is probably miliary dermatitis.

However, all the so-called cutaneous reaction patterns (miliary dermatitis, symmetrical alopecia, head and neck pruritus, and eosinophilic granuloma complex, which includes indolent ulcers, eosinophilic granulomas and eosinophilic plaques) can be seen associated with a flea allergy.

Some cats even start showing signs consistent with one of the reaction patterns, add another variety, go back to the first and so on.

Also, most owners find it difficult to admit there could possibly be a flea problem in their households.

Equally, most believe they are carrying out comprehensive flea control when, in reality, they are using a flea product two to three times a year – unless environmental flea control in addition to adulticides on all pets in the household is used at regular intervals (for example, for imadicloprid, fipronil or selamectin-based products, usually monthly) or oral flea control with fast speed of kill (for example, nitenpyram-based products daily, spinosad or afoxolaner-based products monthly or fluralaner based products every three months).

When an active infestation is detected, environmental flea control is essential to eliminate all life stages as quickly and effectively as possible. If the adulticides are in regular use, additional environmental control should not be needed as the fleas should be killed before they get a chance to lay eggs.

It is therefore important to ask all the pertinent questions about flea control and make sure a comprehensive programme is in place. VNs can play an important part in advising clients about good flea control, taking the particulars of the animal’s situation into account.

Case study: indolent ulcer

Maisy – a four-year-old female, neutered, domestic shorthaired cat – presented with a persistent indolent ulcer affecting her upper lip (Figure 1).

Initially, the lesion had responded to courses of glucocorticoids; however, longer courses were required and the lesions failed to fully respond at some stage. Flea control was not in place as the two cats in the household only went into an outside run, rather than roaming freely.

General clinical examination was unremarkable. Dermatological examination revealed a large

2 / 7 thickened area on the upper lip, which was ulcerated on the surface. No other dermatological signs were seen.

Cytology revealed numerous cocci and some eosinophils and neutrophils. Intense flea control consisting of monthly spinosad for both cats in the household, in conjunction with a household flea spray, was introduced, alongside amoxicillin and clavulanic acid and a course of prednisolone, each for four weeks.

The lesion responded fully and the patient remained in remission with adequate flea control being used lifelong.

Demodex in cats

Young dogs and older dogs with immunosuppressive diseases such as Cushing’s disease or hypothyroidism suffer from demodicosis relatively commonly. In cats, this disease is rare. Demodex cati can cause localised alopecia in cats with immunosuppression.

A contagious form of the disease also exists, with Demodex gatoi being the mite. This parasite often results in pruritic disease and can be hard to find on skin scrapings. Faecal flotation may be the better suited test for pruritic cats, as they over-groom and swallow the parasites.

In a cattery situation, the history often involves a new cat having been introduced into the premises and, subsequently, one or several cats have become pruritic.

Not all cats show pruritus and it may be easier to find the mite on skin scrapings from non-pruritic individuals.

Dermatophytosis in dogs

Ringworm in cats and horses is a relatively frequently diagnosed condition. In dogs, however, it is a much rarer disease. Most lesions we classically think of as ringworm – that is, circular alopecia and erythema – are more commonly associated with a bacterial infection in the dog – they are so-called Staphylococcus rings.

However, dermatophyte infections can occur and can look similar to the disease we know in cats. They can affect the nails and can even present in a way that resembles Pemphigus foliaceus, an autoimmune disease, both clinically, cytologically and even histopathologically.

Although dermatophytosis can be self-limiting – for example, the patient can self cure without any treatments – some patients seem to need intense therapy. This is the case in immunosuppressed dogs in particular and certain body locations – for example, the nails and paw pads – can pose a particular challenge.

3 / 7 It is imperative veterinary nurses are aware of the zoonotic potential and importance of environmental decontamination if dermatophytosis is present in a household. In-house cultures will often be performed and veterinary nurses will usually check these.

It is important to examine the culture plate on a daily basis, as dermatophyte test medium can easily be wrongly interpreted as a positive if, due to fungal growth of environmental contaminants, the colour changes after the colony has reached a certain size.

Case study: Trichophyton mentagrophytes

Figure 2. Missing claws, alopecia, erythema and crusting affecting the paw of Annie, diagnosed with Trichophyton mentagrophytes.

Annie – an eight-year-old Staffordshire bull terrier – presented with a history of two years’ duration of erythema, scaling, alopecia and, more recently, lameness and intense pruritus (Figure 2).

At some stage at the start of the disease, dermatophytes had been cultured in-house. The condition had been successfully treated with topical enilconazole and a negative culture had been obtained prior to discontinuing treatment.

However, more lesions had appeared and Annie had become lame and pruritic. At the time of

4 / 7 presentation, she was receiving prednisolone and regular chlorehexidine/miconazole baths.

General physical examination was unremarkable, apart from the patient being depressed and lame. Numerous patches of alopecia, erythema, scaling and papules were found to affect the head, feet and trunk. Many nails showed onychogryphosis, onychorrhexis and there was paronychia.

Several deep skin scrapings were negative for Demodex canis and microscopy of a hair pluck revealed “dirty looking” hairs. Cytology revealed neutrophils and cocci. A dermatophyte culture grew Trichophyton mentagrophytes.

Annie was treated with itraconazole at a dose of 5mg/kg/day. Adjunctive topical treatment with a miconazole/chlorhexidine shampoo was used to reduce the environmental contamination with fungal spores shed on the hairs. Cephalexin at 25mg/kg was prescribed to treat the secondary pyoderma. The house was thoroughly decontaminated with disinfectants.

Antifungal therapy continued for five months until maximal clinical resolution and two negative fungal cultures at monthly intervals. Despite resolution of infection, scarring alopecia frequently remains in these cases and some small areas of scarring remained in this case. Dermatophytes of the genus Trichophyton are zoophilic and an infection is generally acquired from rodents.

Trichophyton species do not always grow well on dermatophyte test medium (most in-house tests use this medium). Samples should therefore be sent to a qualified diagnostic laboratory.

Dermatophytosis is also a zoonotic disease, so care should be taken – in particular if young children, elderly people or patients with immunosuppression live in the household of an affected dog (or cat).

Symmetrical lupoid onychodystrophy

Figure 3. A close-up of the paw of a dog suffering from symmetrical lupoid onychodystrophy refractory to medical therapy. The picture was taken post-onychoectomy and the wounds are

5 / 7 healing well.

Symmetrical lupoid onychodystrophy (SLO; Figure 3) affects the nails of a dog and is considered to be a reaction pattern, rather than a true autoimmune disease, despite showing histopathological features similar to some autoimmune diseases. SLO usually affects mulitiple claws on all four feet and a breed predisposition exists for German shepherd dogs, Gordon setters, giant schnauzers and Rottweilers.

The condition usually starts at three to eight years of age. At the onset of the disease, often one or two claws are affected, which are lost. This may be confused with traumatic nail loss and a subsequent bacterial infection. However, eventually, most, if not all, the claws are progressively lost.

The affected patient is often severely lame due to pain associated with the loose claws rubbing on the quick.

Once the nail has eventually been lost, a clinical improvement is usually seen quite rapidly, unless other nails are also in the process of shedding.

The most commonly seen clinical signs include onychoschizia, or splitting of the claws; onychogryphosis, which describes an abnormal curvature of the claws; onychomadesis, which stands for the sloughing of claws; and onychorrhexis, used to describe the fragmentation of the claws.

Inflammation of the nail fold, or paronychia, is seen when there is a secondary bacterial infection present. The affected patients do not usually show any other cutaneous or systemic abnormalities.

Several other diseases can present in a similar way and amputation of phalanx 3 with subsequent histopathological examination are needed to diagnose the disease.

However, an experienced dermatologist who has seen many cases of SLO can usually make a visual diagnosis after having ruled out conditions such as dermatophytosis.

Rarely, patients are refractory to treatment and onychochectomy is sometimes considered rather than lifelong immunosuppressive therapy.

Case study: sloughing nails

6 / 7 Figure 4. A close-up of Bruce’s claw at presentation, showing onychoschizia and onychomadesis.

Bruce – a five-year-old male, neutered Rottweiler – presented with a history of sloughing nails (Figure 4). His medical history was otherwise unremarkable. General physical examination was also unremarkable, except he was lame.

Dermatological examination revealed onychomadesis, onychorrhexis, paronychia and onychoschizia affecting most of his claws on all four feet.

Histopathology showed the classical changes of hydropic degeneration of the basal cell layer, lichenoid interface dermatitis and pigmentary incontinence.

Bruce was anaethetised and the loose nails removed. He was discharged with NSAID medication for analgesia and a course of cephalexin at a dose of 30mg twice a day for three weeks. Long-term therapy with high-dose essential fatty acids led to a complete resolution and no relapses were observed.

Please note some of the drugs mentioned within this article are used under the cascade.

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