Dravet syndrome (DS, Online Mendelian Inheritance in Man#607208), or severe myoclonic epilepsy in infancy, is one of the most severe types of genetic epilepsy. Individuals with DS face a high risk of sudden unexpected death in epilepsy. In ≥ 75% of cases, DS is associated with mutations of the gene encoding the α1 subunit of the sodium channel, SCN1A. However, the genetic causes of DS without mutations in SCN1A remain largely unknown.