Mutations in VGSCs are a known cause of neurological disorders such as Dravet syndrome (MIM #607208),37 and multiple de novo mutations in SCN1A, SCN2A and SCN8A have also been observed in patients with epileptic encephalopathies,38 ASD34, 35 and ID.39, 40 None of the probands in the current Bulgarian trio sample with a compound heterozygous genotype in a VGSC suffered from epilepsy. Here, SCN8A is linked to encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.