A 56-year-old, previously healthy man with a 65-pack-year history of cigarette smoking and a family history of lung cancer was admitted on January 8, 2003, with a 3-month history of progressive proximal muscle weakness. This weakness initially was confined to the lower extremities but progressed to involve the upper extremities over a 2-week period. There were no associated complaints of rash or skin discoloration, and dyspnea, cough, or weight loss were not present. His physical examination was remarkable for 2/5 muscle strength in the upper and lower extremities confined to the proximal muscle groups and the absence of skin lesions. Laboratory workup was remarkable for a creatine kinase (CK) of > 17,000 U/L (normal upper limit, 232), absent urine myoglobin, C-reactive protein of 2.1 mg/dL (normal < 0.5), and normal erythrocyte sedimentation rate and antinuclear antibodies. Electromyography and muscle biopsy were consistent with polymyositis, with features suggestive of a paraneoplastic phenomena (Fig 1
). The presence of perivascular and endomysial lymphocytic inflammation in a patchy distribution supported the diagnosis of paraneoplastic polymyositis. There was no evidence of perifascicular atrophy to support dermatomyositis.