In a mouse model of Dravet syndrome, a severe form of childhood epilepsy with high mortality which is commonly caused by heterozygous mutations in NaV1.1, ventricular myocytes surprisingly exhibited an increase in voltage-dependent sodium currents, probably due to an enhanced expression of NaV1.5 (40). The gene discussed is SCN5A; the disease is encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.