[Acute untreated idiopathic polymyositis with cardiac lesions].

An autopsy observation of acute idiopathic polymyositis with the involvement of the sceletal musculature and the heart in a man of 23 who had not been treated with corticosteroids is presented. The main morphological lesions were found in the cross-striated muscles and myocardium. They were characterized by deep degeneration, necrosis, and atrophy of muscle fibers, multiplication of sarcolemma nuclei, massive lymphoplasmo-histiocytis infiltration of the interstitial tissue, active resorbtion by macrophages of the dead muscle cells, the occurrence of giant cells. No disorganization of the connective tissue of the muscles, derma, and the vessels was observed.