A Case of Thyrotoxic Myopathy during Treatment of Thyrotoxic Crisis

Abstract

A 30-year-old Japanese woman had received a diagnosis of Graves' disease 3 years earlier and was treated with thiamazole. However, she discontinued treatment by herself 6 months later. She became aware of emaciation, bilateral leg edema, and dyspnea 4 days before admission. Because of a fever of 39 degrees, she walked to a nearby hospital's emergency room. Physical examination on admission showed a clear consciousness, fever, tachycardia, and enlargement of the thyroid gland. Electrocardiography revealed atrial fibrillation. A chest X-ray film revealed bilateral pleural effusions, pulmonary congestion, and cardiac enlargement. Because thyrotoxic crisis was suspected, she received ventilatory support and was given thiamazole, a potassium iodide preparation, and glucocorticoids. However urinary volume was decreased and serum levels of creatinine, creatinine kinase, and myoglobin were elevated. Acute renal failure due to rhabdomyolysis was suspected. The next day she was transferred to our hospital to undergo hemodialysis. Although her condition improved with intensive care, severe weakness of the proximal limb muscles (manual muscle test 0∼1/5) was shown. The serum potassium level was normal, but electromyography revealed myogenic change suggesting thyrotoxic myopathy. Muscle strength improved through normalization of thyroid function and rehabilitation, and she was discharged on foot. This case suggests that prompt diagnosis and treatment of thyrotoxic crisis are extremely important because the prognosis of thyrotoxic crisis is extremely poor. Moreover, thyrotoxic myopathy should be suspected when limb muscle weakness appears in Graves' disease.