Paraneoplastic pemphigus in a patient with a thymoma

A 76-year-old woman, with a history of thymoma, presented with a painful extensive stomatitis, painful paronychia, lichenoid papules on the hands and superficial erosions on the neck and the trunk. Histological examination showed lichenoid changes, acantholytic blister formation and apoptotic keratinocytes. Direct immunofluorescence was positive for IgG both in the epidermal intercellular spaces and along the basement membrane zone. Indirect immunofluorescence was similarly positive in a pemphigus vulgaris pattern. There was only a partial response to intravenous corticoids. These findings allowed the diagnosis of paraneoplastic pemphigus. The diagnostic characteristics, histopathology and the differential diagnosis of this disease are discussed.