A man had weakness of humeroperoneal distribution associated with limited range of motion of the cervical spine and elbows. At age 25 he developed permanent atrial paralysis, and a cardiac pacemaker was inserted. Although this case was sporadic, most others have been transmitted as an X-linked recessive trait. Mixed patterns in electromyography and muscle histology have caused nosological confusion, but the unique clinical signs seem to define a distinct form of muscular dystrophy, warranting the designation "emery-Dreifuss" type.