Linear IgA bullous dermatosis. Characterization of a subset of patients with concurrent IgA and IgG anti-basement membrane autoantibodies.

BACKGROUND AND DESIGN: The term linear IgA bullous dermatosis defines an immune-mediated blistering skin disease characterized by pruritic blisters, subepidermal separation with neutrophilic infiltration, and linear IgA antibody deposition at the basement membrane zone (BMZ). However, some patients with linear IgA bullous dermatosis demonstrate both IgA and IgG anti-BMZ autoantibodies on immunofluorescence. We describe four such patients and attempt to define this group of patients by studying their clinical, histopathologic, immunopathologic, immunoultrastructural, and immunochemical characteristics.

RESULTS: Clinically, all four patients had a generalized pruritic blistering skin disease consistent with linear IgA bullous dermatosis. Histopathologically, all four cases demonstrated subepidermal blister formation with a predominantly neutrophilic dermal infiltrate. Immunopathologically, tissue-bound IgA (in four of four patients) and IgG (in three of four patients) antibodies were detected at the BMZ. Circulating IgA (in four of four patients) and IgG (in four of four patients) labeled the epidermal BMZ of normal human skin fractured at the lamina lucida and did not label the dermal BMZ. By immunoblot analyses, IgA (in three of three patients) and IgG (in one of three patients) circulating antibodies labeled the 97-kd linear IgA bullous dermatosis antigen. By direct immunoelectron microscopy, IgA and IgG antibodies were localized (in two of two patients) exclusively within the upper lamina lucida of the BMZ.

CONCLUSIONS: Four cases of an immune-mediated blistering skin disease typical for linear IgA bullous dermatosis demonstrated both IgA and IgG anti-BMZ autoantibodies against the linear IgA bullous dermatosis antigen within the upper lamina lucida. We conclude that linear IgA bullous dermatosis should include a subgroup of patients with both IgA and IgG anti-BMZ autoantibodies.