Polymyositis-like syndrome in hypothyroidism: report of two cases

An increase of muscle enzymes in hypothyroidism has sometimes been correlated with a polymyositis-like syndrome and hypothyroid patients have been misdiagnosed and mismanaged as suffering from polymyositis. Actually, muscle symptoms, such as aches and pain, stiffness, weakness and cramps or, more rarely, hypertrophy, are observed in hypothyroidism and increased serum muscle enzyme values, particularly the level of creatine phosphokinase (CPK), indeed seem to suggest polymyositis. The muscular groups most commonly affected by the above mentioned symptomatology are those of the shoulder and pelvic girdles. In this report two hypothyroid patients complaining of muscle symptoms, whose serum muscle enzymes were particularly elevated, are described. In the first case the patient had been suffering from pain and weakness of the thenar eminence for about 4 months. The clinical features suggested a diagnosis of Carpal Tunnel Syndrome, but thyroid function tests revealed primary hypothyroidism. In the second case the patient had been afflicted with muscular weakness of the shoulder girdle for 2 months and was unable to keep his arms raised over his head. A study of thyroid function demonstrated a picture of hypothyroidism. Both patients were treated with L-thyroxine and in a relatively short time biochemical parameters improved remarkably, and the symptoms disappeared. The hypothesis that a muscular effort of long duration by hypothyroid patients may have been responsible for the muscular damage and the symptoms may explain why only a few hypothyroid patients develop a clinical picture similar to polymyositis.