Reports on Scientific Meetings 39

Social Hygiene Symposium 2006

Reported by GJ Chan , TS Cheng , CKM Lam

have intercellular staining pattern on Date: 9 December, 2006 DIF. Pemphigus foliaceus and Venue: Public Health Laboratory Centre, are the most common forms of pemphigus Department of Health, Shek Kip Mei mediated by antibodies to desmogleins 1 and 3. Organiser: Social Hygiene Service, Centre for Desmogleins 1 and 3 are differentially expressed Health Protection, Department of in various layers of the . In majority of Health cases, desmoglein compensation hypothesis predicts the disease phenotype based on antibody profile.

Update on clinical and laboratory is the most common diagnosis for bullous diseases subepidermal blistering disease. It is characterised Speaker: Dr. Chan Po-Tak clinically by intact +/- erosions, Medical and Health Officer, Social Hygiene Service, histopathologically by subepidermal blister and Centre for Health Protection, Department of Health linear IgG and C3 deposition in the basement membrane zone. The molecular targets are two Autoimmune bullous diseases are blistering hemidesmosomal proteins: BP 230 and BP 180. cutaneous diseases due to the development of A common technique employed in the diagnosis autoantibody to components of desmosomes (that of bullous disease is DIF of perilesional mediate keratinocyte cell to cell adhesion) or biopsies. This highlights bound immunoreactants dermoepidermal junction. The majority of the on the biopsied specimen by a fluorescent molecular targets of these antibodies, together with compound conjugated antihuman antibody. By their DNA sequences have been identified. By definition, all immunobullous diseases should have recombinant DNA technology, these molecules a positive DIF; a negative DIF is almost always have been synthesised in vitro and are employed secondary to errors, such as in tissue sampling or in research, diagnosis and disease monitoring. The staining. Indirect immunofluorescence test (IIF) is most common autoimmune bullous diseases in used for estimation of the amount of circulating Hong Kong are bullous pemphigoid, pemphigus anti-skin antibody. A rough correlation is found vulgaris and pemphigus foliaceus. between antibody titre and disease severity in pemphigus vulgaris and foliaceus but not in Pemphigus refers to a group of blistering skin bullous pemphigoid. diseases secondary to the loss of keratinocyte cell to cell adhesion. The major forms are pemphigus With advances in molecular biology, recombinant foliaceus, pemphigus vulgaris, IgA pemphigus and proteins can be produced in vitro. Commercial paraneoplastic pemphigus. Diagnosis requires ELISA kits for desmogleins 1 and 3, BP 180 are clinicopathological correlation and positive direct available for estimation of titre. Such methods have immunofluorescence (DIF) on skin biopsy. All the advantages of being objective, not being 40 Reports on Scientific Meetings substrate dependent (thus less intra-assay and fungal groin infections are acquired from patients' inter-assay variability), provides a continuous score own feet, their feet should be examined for any that reflects the amount of antibody, differentiates involvement and treated accordingly. Central the antibody activity between anti-desmoglein 1 clearing often occurs in while satellite and desmoglein 3, and allows testing of a large or pustule are characteristic of . amount of sample each time. However, the In erythrasma, there is pink fluorescence on Wood's disadvantages of ELISA are that it can only study light examination. A distinct, foul smell is a antibody to one antigen at a time and it is characteristic of group A beta-haemolytic dependent upon the availability of pure antigen. streptococcal intertrigo, an under-recognised cause of intertriginous eruptions in children. For patients with infestation, erythematous papules may be found around axillae. Learning points: Bullous pemphigoid, pemphigus vulgaris Some inflammatory dermatitides affect mainly the and pemphigus foliaceus are the three most flexural skin. In atopic , after the infantile common forms of autoimmune bullous phase, the typical sites of involvement include the diseases in Hong Kong and their diagnosis elbow and knee flexures. requires clinicopathological correlation. The may also affect flexural skin. In infantile identification of most antigenic targets of bullous diseases has facilitated the seborrhoeic dermatitis, salmon-coloured patches understanding of disease pathophysiology with greasy scaling are found in the intertriginous and application in clinical practice in areas and scalp. However, there is no pruritus and improved diagnosis and management. the infant remains healthy and asymptomatic. Irritant occurs more often than the allergic counterpart in flexural site. Common culprits include fragrances, antiperspirants and Flexural dermatoses topical medications. Speaker: Dr. Cheng Tin-Sik Medical and Health Officer, Social Hygiene Service, is sometimes difficult to be differentiated Center for Health Protection, Department of Health from dermatophytosis or eczema in the flexural area. In flexural psoriasis, lesions are bright red Many skin ailments have flexural involvement. with well demarcated margin. The degree of Some entities involve flexures only, e.g. intertrigo; is even throughout the lesion. However, while others also affect non-flexural sites, e.g. silvery scaling is not seen in flexural psoriasis. psoriasis. When the skin affects flexures only, Hidradenitis suppurativa is a chronic suppurative typical features of the skin disease may be lost, and scarring disease in axillae, groin and resulting in diagnostic difficulties, e.g. typical silvery perineum. It usually occurs after puberty and has scaling is usually not found in inverse psoriasis. a female preponderance. Moreover, the clinical picture may sometimes be obscured by maceration and superimposed Some congenital conditions may affect the flexures. infection. Hailey-Hailey disease involves mainly the flexures, presenting as erythematous patches with erosions, , also known as acrochordon, is a very oozing, cracks and fissures. In Darier's disease, common condition affecting the skin flexures. It brown keratotic papules are found mainly in usually occurs after 30 years of age. Common seborrhoeic areas; however, the flexures may fungal infections over flexural skin include also be involved. Axillary freckling is almost dermatophytosis and candidiasis. As almost all pathognomonic of neurofibromatosis. Reports on Scientific Meetings 41

Malignant conditions may also affect the flexures. complex interactions between environmental Langerhans' cell histiocytosis can mimic factors and an individual's genotype, but is also a seborrhoeic dermatitis but perifollicular purpura holistic representation of human body as a whole. may be found. Extramammary Paget's disease may also involve axillary or anogenital skin. It is Skin is an effective and readily available indicator important to screen for the presence of any of serious diseases. Even an untrained observer underlying carcinoma in this condition. Symmetric, should be able to recognise the pale, ashen dark brown, dried skin with velvety surface is found appearance of a patient in shock, the cyanosis in . When associated with associated with cardiac failure, or jaundice as the underlying malignant diseases, acanthosis first sign of obstructive biliary disease. A complete nigricans develops more rapidly and suddenly with physician, however, must also be able to detect oral mucosa involvement and hyperkeratosis of the more subtle skin signs of life threatening palms and soles. Pseudoacanthosis nigricans, a diseases. None of these changes should be benign flexural dermatosis, is usually associated overlooked or disregarded, as these are the with obesity and resistance. callings for our intervention. In addition, as clinicians, we know that dermatologic disorders are significant causes of human suffering.

Learning points: Examples of various cutaneous manifestations Flexural skin is thin. It is a semi-occluded of systemic diseases were given. They can be area and is prone to formation of striae and classified as 1) nutritional: protein, vitamins, fatty atrophy. Thus when topical steroid is used acids, Fabry disease, lipoid proteinosis; in flexural dermatoses, milder agent is 2) cutaneous mineralisation and ossification, usually employed. It is also important to keep the flexures dry and correct any porphyria; 3) heritable disorders of connective possible exacerbating factors such as tissue with skin changes; 4) heritable diseases with infection, excessive sweating and increased sensitivity to cellular injury, basal cell incontinence when dealing with flexural naevus syndrome; 5) neoplastic diseases: dermatoses. Langerhans' cell histiocytosis, cutaneous nonhistiocytoses X, the mastocytosis syndrome, carcinoid; 6) cutaneous manifestations according to system: haematologic, gastrointestinal, Cutaneous manifestations of hepatobiliary, renal, cardiopulmonary, peripheral systemic diseases vascular, endocrine, neurocutaneous and Speaker: Dr. Hau Ka-Lam rheumatological diseases; 7) skin changes and Medical and Health Officer, Social Hygiene Service, diseases in pregnancy; 8) inflammatory diseases: Centre for Health Protection, Department of Health Behcet's disease, scleredema; 9) paraneoplastic syndromes. Skin is sometimes involved in systemic disease. By appreciating cutaneous manifestations of systemic diseases, physicians can better determine the most Learning points: appropriate management or need for referral to Systemic diseases can present to dermatologists. has also been a dermatologist with a variety of skin major beneficiary of the advances in cell and manifestations. These should be recognised molecular biology, immunology, and genetics early in order to provide early intervention of serious underlying diseases. during the past several decades. Many of the skin diseases we deal with daily are related not only to