Pemphigus foliaceus masquerading as IgA pemphigus and responding to dapsone

A 14-year-old male presented with seven years history of recurrent episodes of fluid filled, itchy and eroded lesions over the body not responding to oral corticosteroids and azathioprine. Dermatological examination revealed crusted plaques and erosions in a seborrheic distribution. Histopathology of skin lesions and direct immunofluorescence were characteristic of pemphigus foliaceus. He was treated with dexamethasone pulse therapy with inadequate response. However, relapsing skin lesions revealed a circinate arrangement with a predilection to trunk and flexures. In view of clinical features suggestive of IgA pemphigus, he was started on dapsone, to which he responded dramatically in four weeks. However, repeat biopsy continued to reveal features of pemphigus foliaceus and ELISA for anti-desmoglein 1 antibodies was positive.