A subepidermal blistering dermatosis associated with coexistent IgG and IgA anti-dermal basement membrane zone antibodies; demonstration of IgG antibodies reactive against a 200-kDa dermal antigen.

We report a 66-year-old woman presenting with an annular erythematous and bullous eruption. Her clinical and histological findings were similar to those of linear IgA bullous dermatosis or dermatitis herpetiformis. Direct immunofluorescence revealed linear deposition of IgA, IgG and C3 along the basement membrane zone (BMZ). Indirect immunofluorescence detected IgG and IgA antibodies against the BMZ. Salt-split skin technique demonstrated that IgG antibodies bound exclusively to the dermal side, while IgA antibodies bound not only to the dermal side, but also to the epidermal side with relatively weak intensity. On immunoblot analysis, the patient's IgG antibodies exclusively reacted with a band of 200-kDa, while the antigenic target of IgA antibodies was not identified. The present case is thought to be a unique bullous dermatosis mediated by both the IgG antibodies to a novel 200-kDa antigen and IgA antibodies against undetermined antigens.