Coexistence of scleromyositis associated with PM-Scl antibody and myasthenia.

Myasthenia gravis coexists in about 15% of the cases with other autoimmune diseases. Association with polymyositis or dermatomyositis is very rare, although myasthenic reaction is not infrequent in typical polymyositis and myopathic changes may occur in cases of myasthenia. This is the first case of coexistence of myasthenia and scleromyositis, associated with PM-Scl antibody as an immune marker. The patient was found to have persistent thymus. Myasthenia preceded scleromyositis for 9 yr, was at periods asymptomatic, and recurred simultaneously with development of scleromyositis. Scleromyositis should be added to the list of autoimmune disorders coexistent with myasthenia.