Heart muscle disease in familial hypokalaemic periodic paralysis

The case history, skeletal muscle and heart muscle biopsy findings from an affected member of a family suffering from hypokalaemic periodic paralysis associated with permanent muscular weakness are reported. The patient, a female aged 35 years, while treated with 750 mg and later 1000 mg of acetazolamide daily, developed typical exercise angina pectoris. The ECG during exercise showed ST-segment depression. A coronary angiography was performed because coronary artery disease was suspected. To exclude cardiac muscle disease a biopsy of the left ventricular wall was taken. The angiography was normal. Ultrastructural analysis of the biopsy specimen showed an unusual amount of intermyofibrillary glycogen resembling, although far less abundant, the increase of glycogen found in the skeletal muscle biopsy specimen obtained from the same patient. The possible implications of these findings are discussed with reference to the normal echocardiographic findings in the family.