Pemphigus foliaceus in a patient with rheumatoid arthritis and Sjögren's syndrome. A case report.

A 74-year-old male patient with rheumatoid arthritis and Sjögren's syndrome developed pemphigus foliaceus. Clinically healthy skin tissue revealed a fluorescent band of IgM along the basal membrane and an intercellular deposit of C3 and IgG in the deepest areas of the epidermis. Similar investigations of diseased skin revealed no deposits of IgM, and C3 and IgG were spread over a large area of the epidermis, though following the same pattern. In sero-positive rheumatoid patients with and without vasculitis, C3 and IgM are frequently found in small dermal vessels immediately below the epidermis in apparently normal skin. The fluorescent band of IgM along the basal membrane is thought to be an expression of the patient's rheumatoid arthritis, in spite of the fact that this IgM site is not typically associated with rheumatoid arthritis. The change in the pattern of deposition is thought to be due to pemphigus foliaceus.