[Perifascicular necrosis and regeneration in a case of adult polymyositis]

We report a case of adult polymyositis with peculiar muscular pathology of innumerable muscle fiber necrosis and regeneration accentuated in the perifascicular area. A 51-year-old woman developed generalized weakness of the extremities, trunk and bulbar muscles subacutely for two months. Anterior tibial muscle biopsy showed numerous tube-like necrotic/regenerative muscle fibers predominantly in the perifascicular area. The diameters of the muscle fibers were smaller in the periphery of the fascicles. Small arteries at the center of the fascicles occasionally showed marked perivascular cuffing, although complement component C9 was negative in the vessel wall. The gradient of the diameters of necrosis/regeneration fibers was thought to have been caused by ischemia of the muscles, which persisted at the perifascicular area leading to recurrent necrosis and regeneration and gradually invaded towards the center of the fascicles. We designated this muscular pathology as perifascicular necrosis and regeneration, and regarded it was an acute severe form of the perifascicular ischemic lesions of myositis.