Primary synovial chondromatosis of the subtalar joint affecting two brothers.

Primary synovial chondromatosis is a rare benign condition characterized by the formation of multiple cartilaginous nodules in the synovium of joints and on occasions tendon sheaths or bursae. A case of primary synovial chondromatosis affecting the subtalar joint is reported. The patient's brother developed the same condition affecting the same joint 2 years later. The proposed etiologies are discussed including the presence of the proto-oncogene C-erb B-2.