Drug-induced linear IgA disease: target antigens are heterogeneous.

No information is available concerning the target antigen(s) in drug-induced linear IgA disease. The purpose of this study was to define better drug-induced linear IgA disease by studying its immunopathological, immunoultrastructural and immunochemical characteristics in three patients. In the first patient, IgA deposits were seen in the lamina lucida. In the second and the third patients, IgA deposits were seen on each side of the lamina densa. Immunoblotting of the first patient's serum showed that IgA reacted with a protein of 230 kDa similar to the bullous pemphigoid-associated antigen 1 (BPAG 1). The second patient's serum did not react with specific bands. In the third patient IgA antibodies reacted with a protein of 97 kDa on epidermal extracts. Our findings suggest that, as in idiopathic forms, the target antigen is not unique in drug-induced linear IgA disease. In some patients, drug-induced linear IgA disease may represent an IgA class response to the BPAG 1.