Idiopathic Giant Cell Polymyositis

Eight months after removal of an asymptomatic thymoma of a mixed cell type, a 57-year-old woman developed generalized muscle weakness. Serum creatine phosphokinase and aldolase levels were elevated, electromyogram showed myopathy, and muscle biopsy disclosed giant cell myositis. Response to anticholinesterase compounds and electromyography indicated concomitant myasthenia gravis. The electrocardiogram showed ST segment and T wave changes. The patient's illness was managed with anticholinesterase compounds and corticosteroids with difficulty because of fluctuating effectiveness. She died five years and two months after thymectomy. Postmortem examination revealed giant cell myositis, myocarditis, and lymphoid cell infiltration in the thyroid. Thymic tissue was not found. This patient is one of 13 reported patients with a unique syndrome consisting of idiopathic giant cell polymyositis, thymoma, myocarditis and, frequently, myasthenia gravis and thyroid abnormality.