SCN4A and Myotonia: Neonatal laryngospasm and unusual distribution of myotonia and other NDM signs have also been reported in several NDM patients, who have been shown to carry different SCN4A mutations, such as G1306E, I693T, A799S, N1297K, and T1313M (although not all patients that carry these mutations show childhood or neonatal respiratory problems) (78, 94–99).