Elevated muscle enzymes in a patient with severe hypocalcemia mimicking polymyositis

Abstract We report a case of hypocalcemic myopathy confounded by polymyositis due to an elevated level of serum creatine kinase (CK). A 30-year-old man was referred to our hospital for the treatment of provisionally diagnosed polymyositis. His presentation with tetany, hyporeflexia, and general fatigue, in addition to muscle weakness on admission, prompted us to scrutinize a blood sample in search of secondary myopathy. Blood chemistry revealed an elevated level of serum CK, marked hypocalcemia, hyperphosphatemia, and a low serum level of intact parathyroid hormone. The Ellsworth Howard test confirmed the diagnosis of hypoparathyroidism. Supplementation with calcium and 1α-hydroxyvitamin D3 improved his muscle weakness rapidly, and his serum CK level returned to the normal range. Hypoparathyroidism should be included in differential diagnoses of elevated serum CK.