[Polymyositis with rimmed vacuoles in a case of chronic thyroiditis].

We report a 37-year-old woman who developed chronic thyroiditis, and polymyositis with rimmed vacuoles (RVs). She developed paresthesia of glove and stocking type, muscle weakness of the lower extremities, and slowness in motion. On examination, her lower legs were atrophic and weak, more prominent on the right, while proximal muscles in the upper and lower extremities were slightly affected. Deep tendon reflexes of the upper and lower extremities were normal except for the absent Achilles tendon reflexes. Serum CK was high (1,809 IU/l), and laboratory data indicated chronic thyroiditis and hypothyroidism. Muscle CT showed severe fatty changes in the gastrocnemius and soleus muscles, more marked on the right, and slight atrophy of the thigh muscles. Electromyography and nerve conduction velocity study revealed peripheral neuropathy. Muscle biopsy revealed numerous myofibers with RVs, together with myofiber necrosis, phagocytosis and lymphocyte infiltration, consistent with myositis. Nerve biopsy was indicative of slight axonal degeneration. A diagnosis of polymyositis with RVs in combination with chronic thyroiditis was made. Prednisolone combined with levothyroxine markedly improved muscle weakness though atrophy and weakness of the lower legs were barely improved. Distal-dominant asymmetric affection of the leg muscles and many myofibers with RV on the biopsied muscle are atypical and rare findings of polymyositis. Associated chronic thyroiditis and neuropathy may be related to the formation of marked rimmed-vacuolar degeneration of myofibers in the present case.