The SCN8A gene encodes the sodium voltage-gated channel alpha subunit 8. Mutations in this gene have been associated with early infantile epileptic encephalopathy type 13. With the use of whole-exome sequencing, a de novo missense mutation in SCN8A was identified in a 4-yr-old female who initially exhibited symptoms of epilepsy at the age of 5 mo that progressed to a severe condition with very little movement, including being unable to sit or walk on her own.
Keywords: absent speech; action tremor; appendicular hypotonia; blepharospasm; broad forehead; bulbar palsy; developmental regression; developmental stagnation at onset of seizures; dysphagia; epileptic encephalopathy; exaggerated startle response; failure to thrive in infancy; full cheeks; gastroesophageal reflux; gastrostomy tube feeding in infancy; generalized tonic seizures; generalized tonic-clonic seizures on awakening; gingival overgrowth; hypoxemia; infantile axial hypotonia; intellectual disability, severe; neck muscle weakness; no social interaction; obstructive sleep apnea; respiratory difficulties.