Severe neonatal episodic laryngospasm due to de novo SCN4A mutations: a new treatable disorder.

Abstract

Myotonia is unusual in infants, and not well-known. We describe neonatal life-threatening features of myotonia caused by de novo mutations in the muscle sodium channel gene SCN4A. Three male neonates initially displayed episodic laryngospasms, with face and limb myotonia appearing later. We found SCN4A de novo mutations in these neonates: p.Gly1306Glu in 2 unrelated cases and a novel mutation p.Ala799Ser in the third. Two patients survived their respiratory attacks and were efficiently treated by sodium channel blockers (mexiletine, carbamazepine) following diagnosis of myotonia. Severe neonatal episodic laryngospasm is a new phenotype caused by a sodium channelopathy, which can be alleviated by channel blockers.