Ataxia-telangiectasia associated with sarcoidosis.

Ataxia-telangiectasia and sarcoidosis are diseases characterized by abnormalities of the immune system. We examined a 13-year-old female with ataxia-telangiectasia who developed atrophic, violaceous plaques of the skin and a destructive, polyarticular arthritis. The histologic features of both skin and synovium were most consistent with a diagnosis of sarcoidosis. Interaction of these two immunologic disorders may have resulted in the unusual features of this patient's disease.