Pathogenesis of heart block in a fatal case of dermatomyositis.

Approximately 70% of patients with dermatomyositis have evidence of cardiac damage; in one third of cases this affects principally or solely the conduction tissue. In infants similar histological lesions have been associated with a maternal autoantibody, anti-Ro, that crosses the placenta and produces congenital heart block. Anti-Ro antibody was detected in a fatal case of dermatomyositis with lesions of the conduction system.