Second, it is now apparent that while 70–80% Dravet syndrome patients have SCN1A mutations, mutations in other genes such as SCN1B, SCN2A, SCN8A, PCDH19, GABRA1, GABRG2, STXBP1, CHD2 genes can cause Dravet syndrome like phenotypes [98], which would be missed if only SCN1A was sequenced. This evidence concerns the gene SCN1B and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.