SCN9A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy: Heterozygous mutations in the SCN9A gene have previously been associated with generalized epilepsy with febrile seizures (OMIM#613863) and Dravet syndrome (severe myoclonic epilepsy of infancy, OMIM#607208) when accompanied by mutations in the SCN1A (Sodium channel, neuronal type 1, alpha subunit, OMIM*182389) gene54, 55.