There are two forms of pemphigus foliaceus. The two forms are clinically and histologically similar, but present epidemiological differences. The first, non-endemic form was initially described in Paris in 1844 and has a cosmopolitan distribution (Cazenave's pemphigus foliaceus). This form occurs frequently in Jews. The second form is locally endemic in rural areas of Brazil, El Salvador, Argentina, Paraguay, Bolivia, Venezuela, Peru, Colombia and (?) Tunisia. The disease was initially described in 1903. In view of the fact that the condition also occurs outside Brazil, the name "Brazilian pemphigus" is unfortunate and is increasingly falling into disuse. There are major clusters in the Brazilian states of Goias, Mato Grosso do Sul, Parana and Sao Paulo. On the Atlantic coast where the greatest proportion of the Brazilian population lives the disease is very infrequent.

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Epidemiological studies point to a provoking antigen in the environment, but to date its nature has not been established. The "trigger" appears to be based on immunological mimicry between an environmental antigen and desmoglein 1 with cross reactivity as a consequence. The antigen appears to have a limited geographical distribution. There is an association with certain HLA-DR alleles, but genetic factors are probably not the only explanation in view of the fact that the disease can develop in various ethnic groups. Possibly a sensitisation period is required. Urbanisation markedly reduces the incidence of the disease. There is no person-to-person transmission, including no mother-to-child transfer, in contrast to what is seen regularly in pemphigus vulgaris.

Endemic pemphigus foliaceus is a dermatological auto-immune disease. The disease is characterised by superficial vesicles and blisters. In Brazil, endemic pemphigus is known as "fogo selvagem" ("wild fire"), which refers to the burning feeling that patients describe. The disease principally affects children and young adults, which differs clearly from Cazenave’s pemphigus foliaceus which occurs principally in adults. The course can be acute (< 6 weeks), chronic (> 6 weeks) or recurrent (partial remission). A further distinction is drawn between localised, generalised and hyperpigmented forms. The disease usually begins gradually with progressive skin lesions over a period of weeks to months. The course is rarely fulminant. The lesions can persist for years. Nikolsky’s sign is usually present, as in pemphigus vulgaris. When pressing laterally on healthy skin, in the area of a skin lesion, the uppermost layer can be easily detached (Nikolsky’s phenomenon I). This points to the reduced cohesion of the keratinocytes in the epidermal tissue. When pressing on top of a blister, the contents can be dispersed laterally in the epidermis (Nikolsky’s phenomenon II). Nikolsky’s sign is absent during remission.

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In the generalised forms, three classes can be distinguished: (1) an acute, aggressive, bullous, exfoliative form. This form can be life-threatening if a Kaposi's varicelliform eruption occurs (not to be confused with Kaposi's sarcoma); (2) exfoliative erythroderma with confluent superficial erosive exudative lesions with crust formation; (3) keratotic plaques and nodules which can resemble nodular prurigo. The lesions are often found on the scalp, face, back and chest. The mucous membranes are spared. Hyperpigmentation can occur when the patient goes into remission. Hyperpigmentation can be limited to the sites where the erosions occur or can be dramatic and generalised, even on previously normal skin. It is described that Caucasians then resemble mulattoes, mulattoes resemble blacks and that blacks acquire a blue-grey tint. There is also an increase in the number of melanocytes with an accumulation of melanin. There are sporadically associated dwarf growth, azoospermia and mental abnormalities (patients are quiet and isolated, non-communicative and depressive). This requires further study.

Immunological abnormalities are found consistently. IgG auto-antibodies against keratinocytes are detectable in skin biopsies and in serum. A skin biopsy shows typical splitting under the stratum corneum, as well as positive immunofluorescence staining for IgG there. In contrast, in pemphigus vulgaris antibodies can be detected throughout the whole epidermis. Antibodies are often also detected in oral and oesophageal mucosa, although macroscopically these tissues are normal. The reason for this remains unanswered. Cytology of a blister smear shows acantholytic epidermal cells, so-called pemphigus cells or Tzanck cells. Auto-antibodies against desmoglein 1 can be detected by ELISA. There is a good correlation between the titre in the serum and disease activity. The test has a high specificity. The antibodies can be present for one to four years before clinical lesions appear. If the disease becomes clinically apparent, the concentration of antibodies increases tenfold on average. Whether antibodies against other epidermal antigens (e.g. against plakoglobin) play a role is unclear.

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Indirect immunofluorescence is reliable if calcium is present in the buffer. The antigen epitope apparently needs calcium in order to be detected. The keratinocyte surface antigen in fogo selvagem is a desmosomal glycoprotein known as desmoglein 1. This term refers to "desmo" (desmosome) and glein (glue). It is assumed that the antigen is a cell adhesion molecule. Desmoglein 1 antibodies are also found in Cazenave's pemphigus foliaceus. Other immunological abnormalities are also found, such as high titres of a -thymosine, a substance necessary for the maturation of T cells. There are no anti-DNA antibodies and the antinuclear factor (ANF) is negative. Almost all patients have either DR4 or DRw6 in their HLA phenotype. In a study of 2686 people with fogo selvagem, there were 485 cases in which more than one person in a family had the condition. In these cases, the disease occurred in genetically related people (e.g. father-son, brother-sister) in 93%, but in only 7% where the family members were not related (e.g. husband-wife). This points to a genetic predisposition.

Differential diagnosis includes bullous pemphigoid, herpes gestationis, systemic lupus erythematosus, Hailey-Hailey disease (benign familial chronic pemphigus), Darier's disease, drug side effects and a paraneoplastic syndrome. There are several characteristics that distinguish pemphigus foliaceus from pemphigus vulgaris. Pemphigus vulgaris occurs only sporadically in adults (no familial clustering). The skin lesions are found deeper in the skin, mucosal lesions are common and the prognosis is guarded. Pemphigus foliaceus, however, occurs more in children and young adults and does show familial clustering. Mild forms can resemble discoid lupus erythematosus, but there is no atrophy, no follicular plugging and no hypopigmentation in endemic pemphigus.

Before the availability of cortisone, mortality was 5-40%, but with treatment it is markedly reduced. Treatment consists of prednisolone, 60-90 mg daily until no more new skin blisters are formed. Potassium permanganate is used topically. Treatment usually lasts two years. Immunosuppressants are also used, as in pemphigus vulgaris. If no more lesions occur for 12 months, the patient is considered cured.