SCN1A is regarded as the most important epilepsy gene associated with a spectrum of epilepsy syndromes ranging from milder phenotypes in generalized epilepsy with febrile seizures plus (GEFS+) to severe myoclonic epilepsy of infancy (Dravet syndrome). Here, SCN1A is linked to encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.