Familial severe myoclonic epilepsy of infancy: truncation of Nav1.1 and genetic heterogeneity.

Background: Severe myoclonic epilepsy of infancy (SMEI) or Dravet syndrome has been long suspected of having a genetic origin. Recently, mutations in SCN1A and GABRG2 have been described in SMEI patients. The sporadic nature of the SMEI syndrome and the occurrence of SCN1A and GABRG2 mutations in a mild familial phenotype, termed generalized epilepsy with febrile seizure plus complicates genotype-phenotype correlations.