Calcium is essential for proper muscular function and metabolism. Myopathy with high creatinkinase activity can be a rare manifestation of hypocalcemia of various origin, such as vitamin D deficiency, hypoparathyroidism, pseudohypoparathyroidism (PHP). 16-year old previously healthy boy was admitted to intensive care unit with convulsions lasting for three minutes and a transient loss of consciousness. Laboratory results revealed severe hypocalcemia (total S-Ca < 1.0 mmol/L; normal 2.2–2.6

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... L), hyperphosphatemia (S-P 2.8 mmol/L; normal 0.6–1.6 mmol/L). Serum creatinkinase (S-CK) activity was 32 μkat/L (normal 0.57–2.45 μkat/L). Other basic biochemical parameters including creatinine, troponin, alkaline phosphatase were within normal values. Calcemia was gradually corrected within two weeks by intravenously and orally administered calcium and by cholecalciferol. S-CK reached a maximum of 222 μkat/L on day 4 and dropped to 7.2 μkat/L on day 14. Boy had no myalgias, neither clinical signs of myopathy. Echocardiography was normal with normal myocardial contractility, without any signs of calcification. The serum level of parathyroid hormone (S-PTH) was high (12 pmol/L; normal 0.7–5.5 pmol/L), fully compatible with the diagnosis of PHP. Molecular analysis revealed pseudohypoparathyroidism type Ib (PHPIb).In conclusion, manifest tetany and even mild myopathy with very high S-CK can occur in hypocalcemic patients and usually resolves after normalization of hypocalcemia.