Subcorneal pustular dermatosis-type IgA pemphigus induced by thiol drugs

We report a case of subcorneal pustular dermatosis (SPD)-type IgA pemphigus arising in a 49 year-old woman with rheumatoid arthritis who had been treated with chrysotherapy. Scaly erythemic plaques containing vesicles and pustules occurred on her chest and abdomen during the course of anti-rheumatic treatments using prednisolone at 11 mg/day and thiol compounds (bucillamine and gold sodium thiomalate). Histological investigations revealed subcorneal pustules containing many neutrophils and a few acantholytic cells, and intercellular IgA deposits at the upper epidermis of the eruptions without any other immunoglobulins and complement component C3. Circulating IgA antibodies directed against intercellular spaces of the epidermis were found by prolonged incubation of normal skin specimens in medium containing 20% patient's serum in an explant culture, although standard indirect immunofluorescence for IgA antibodies was negative. The eruptions were treated successfully with prednisolone, 30 mg/day, dapsone, 50 mg/day, and discontinuance of the thiol compound. In addition to the coexistent rheumatoid arthritis, both thiol compounds might have been responsible for the development of the eruptions.