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Pemphigus is a group of chronic autoimmune skin diseases characterized by blister formations on the outer layer of the skin and the mucous membranes. Three clinical forms have been characterised, of which pemphigus vulgaris is the most frequent (75%).
Prevalence is estimated at approximately 1/2,630.
Onset occurs on average at 50-60 years, although childhood onset forms have been described. The disease begins with blisters (bullae) in the mouth, which are often mistaken for aphtae. The blisters are flaccid and are easily broken, leading to often painful lesions or erosions. Blistering can also affect the oesophagus, rectum, nose or the lining of the eyelids. Skin lesions appear several weeks or several months after the onset of mucosal erosions. Nikolsky's sign can appear on perilesional skin or, in some cases, even on healthy skin. Pemphigus vegetans is a clinical variant characterised by intertriginous lesions developing into vegetating plaques.
The exact causes of the disease are unknown. Autoantibodies directed against desmosome components cause acantholysis and intraepidermal cleft. In pemphigus vulgaris, autoantibodies bind to desmogleine 1 and 3 (keratinocyte membrane molecules).
Diagnosis should be considered in the presence of bullae on chest or scalp. It can be confirmed by standard histopathological analysis and direct immunofluorescence test. Intraepidermal blisters due to suprabasal acantholysis and IgG (mostly IgG1 and IgG4) and/or C3 complement deposits can be detected at the cell surface of keratinocytes. The disease grade is correlated with the level of circulating antibodies.
Management and treatment
Systemic steroid therapy, given as a 12-month course in absence of relapse, is the treatment of choice. It can be combined with immunosuppressant drugs.
The prognosis of pemphigus has markedly improved over the last decades with steroid therapy. Nevertheless, mortality remains an issue (5% of cases). In these cases, death occurs during the first years of disease progression, mostly as a consequence of treatment-related systemic infections and in a smaller proportion, as a consequence of superinfected lesions.
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