De novo variant in SCN4A causes neonatal sodium channel myotonia with general muscle stiffness and respiratory failure

Neuromuscul Disord. 2019 Nov;29(11):907-909. doi: 10.1016/j.nmd.2019.09.001. Epub 2019 Sep 13.


Variants of the skeletal muscle sodium channel gene SCN4A are associated with different neuromuscular disorders including sodium channel myotonia. Here, we report an infant with a de novo variant in SCN4A presenting with neonatal onset of severe muscle stiffness with involvement of facial and eyelid muscles, and life-threatening events with respiratory failure due to severe apnoea and thorax rigidity. The boy dramatically improved in both respiratory and motor function under carbamazepine therapy.

Keywords: Muscle stiffness; Myotonia; Respiratory failure; SCN4A.

Publication types

  • Case Reports

MeSH terms

  • Elasticity
  • Genetic Variation*
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Muscular Diseases / genetics*
  • Muscular Diseases / physiopathology
  • Muscular Diseases / therapy
  • Myotonia Congenita / genetics*
  • Myotonia Congenita / physiopathology
  • Myotonia Congenita / therapy
  • NAV1.4 Voltage-Gated Sodium Channel / genetics*
  • Phenotype
  • Respiratory Insufficiency / genetics*
  • Respiratory Insufficiency / physiopathology
  • Respiratory Insufficiency / therapy


  • NAV1.4 Voltage-Gated Sodium Channel
  • SCN4A protein, human

Supplementary concepts

  • Potassium aggravated myotonia