Mixed immunobullous disease: is this linear IgA disease?

We report five patients who demonstrated clinical, histological and direct immunofluorescence (IF) features typical of linear IgA disease (LAD), but who also displayed IgG anti-basement membrane zone (BMZ) antibodies on indirect IF. The presence of circulating IgG anti-BMZ antibodies is often said to exclude the diagnosis of LAD. Unable to confidently classify these patients, we reviewed their clinical progress for unifying features. This revealed an almost universal benefit from dapsone therapy. We therefore propose that when strong linear IgA deposition is observed at the BMZ, a first line trial of dapsone is indicated, irrespective of the presence of circulating IgG. The class of antibody fixed in vivo appears to influence the clinical picture more than the class of circulating antibody.