SCN1A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy: Interestingly, in Dravet syndrome (Dravet, 1978), a severe encephalopathy due to de novo loss-of-function mutations in the SCN1A gene, leading to haploinsufficiency of NaV1.1 channel (reviewed by Brunklaus and Zuberi, 2014), epilepsy typically presents around 6 months of age.