Three cases of linear IgA/IgG bullous dermatosis showing IgA and IgG reactivity with multiple antigens, particularly laminin-332.

IMPORTANCE: Linear IgA/IgG bullous dermatosis (LAGBD) is a relatively rare autoimmune bullous disease characterized by both IgA and IgG antibodies to epidermal basement membrane zone. The heterogeneity and pathogenesis of the LAGBD autoantigens have not been fully elucidated. OBSERVATIONS: We report 3 Japanese cases of LAGBD (ages 81, 88, and 64 years; 1 woman and 2 men). The patients showed bullous and erosive lesions on the trunk and extremities with minimal mucosal lesions. Histopathological analysis revealed a subepidermal blister with neutrophilic infiltration with eosinophils in 2 cases. Direct and indirect immunofluorescence studies disclosed IgG and IgA antibasement membrane zone antibodies. In immunoblot analyses of various antigen sources, all cases showed IgG and IgA antibodies to various subunits of laminin-332, in addition to IgG and IgA reactivity with type VII collagen, laminin-γ1, and BP230 and BP180 recombinant proteins. CONCLUSIONS AND RELEVANCE: Our studies revealed that the 3 LAGBD cases showed prominent IgG and IgA reactivity with laminin-332, which was only rarely reported. In addition, all cases showed IgG and IgA reactivity with other multiple antigens, indicating the role of epitope-spreading mechanisms initiated from laminin-332. The significance of IgA antibodies to laminin-332 should be studied in larger cohorts of both LAGBD and linear IgA bullous dermatosis.