IgA bullous pemphigoid: a distinct blistering disorder. Case report and review of the literature.

We report a patient with an eccrine carcinoma who developed localized blistering which clinically resembled pemphigoid, histologically showed subepidermal blistering with features of both dermatitis herpetiformis and bullous pemphigoid, responded to dapsone and exhibited linear IgA deposition on direct immunofluorescence. The nosological position of patients with linear IgA deposition and subepidermal blistering is not clear. A review of the literature reveals that in adults linear IgA deposition may occur in three separate situations: dermatitis herpetiformis, bullous pemphigoid and a third condition of which our case is an example which is best termed IgA bullous pemphigoid. This condition is distinguished from cases of dermatitis herpetiformis with linear IgA by the clinical features and the site of IgA deposition on immunoelectronmicroscopy. It is distinguished from cases of bullous pemphigoid with linear IgA by the absence of circulating IgG antibasement membrane zone antibody, the therapeutic response to dapsone and the frequent occurrence of circulating IgA antibasement membrane zone antibody. IgA bullous pemphigoid has not previously been reported with a carcinoma but the association lends further support to the concept that this eruption represents a variant of pemphigoid.