A rare case of unilateral adrenal hyperplasia accompanied by hypokalaemic periodic paralysis caused by a novel dominant mutation in CACNA1S: features and prognosis after adrenalectomy

A 43-year-old Han Chinese male presented with severe hypokalaemic paralysis that remitted after taking oral potassium. The patient had suffered from periodic attacks of hypokalaemic paralysis for more than 20 years. A computed tomography (CT) scan of the abdomen showed a nodular mass on the left adrenal gland, although laboratory examination revealed the patient had not developed primary aldosteronism. The patient underwent a left adrenalectomy 4 days after admission, and the pathological examination further confirmed a 1.1 cm benign nodule at the periphery of the adrenal gland. Three months after the adrenalectomy, a paralytic attack recurred and the patient asked for assistance from the Department of Medical Genetics. His family history showed that two uncles, one brother, and a nephew also had a history of periodic paralysis, although their symptoms were milder. The patient’s CACNA1S and SCN4A genes were sequenced, and a novel missense mutation, c.1582C > T (p.Arg528Cys), in CACNA1S was detected. Detection of the mutation in five adult male family members, including three with periodic paralysis and two with no history of the disease, indicated that this mutation caused hypokalaemic periodic paralysis type I in his family. Follow-up 2 years after adrenalectomy showed that the serum potassium concentration was increased between paralyses and the number and severity of paralytic attacks were significantly decreased.