Linear IgA dermatosis: report of an infantile case and analysis of 213 cases in Japan.

A 3-year-old boy presented with multiple vesicles, showing a rosette-like arrangement around the crusts. Histopathological and immunohistochemical examinations demonstrated subepidermal blistering with neutrophilic infiltration associated with deposition of IgA, but not IgG, linearly distributed along the basement membrane zone (BMZ) of the epidermis. Indirect immunofluorescence revealed circulating antibodies (IgA class, x160) against the BMZ of guinea pig lip skin. Based on the diagnosis of linear IgA dermatosis (LAD) of childhood, administration of dexamethasone (2 mg/day) was started, and the eruptions diminished immediately. Western blot analysis using extract of the HaCaT cell as a substrate, demonstrated the corresponding antigen at 120-kDa molecular weight. There have been 213 cases of LAD reported in Japan including conference abstracts and these were studied to determine whether infantile cases differed from adult ones, and whether cases associated with IgG as well as IgA (IgA/G type), differed from the cases associated with IgA only (IgA type). IgG contributed less frequently to the infantile type (age of onset, < or =15 years) than to the adult type (age of onset, > or =16 years). Clinical appearance did not show any obvious difference between the IgA/G type and IgA type. However, three-quarters of cases showing localization of antigen to the dermal side were the IgA/G type.