WES analysis of the eight trios led to the identification of unique de novo candidate RTT-L mutations in genes known to cause childhood epilepsy (KCNB1, KCNQ2, and GABRG) [52,60,61,62], mental retardation (GRIN1 and GRIN2A) [63,64], hemiplegia, developmental and epileptic encephalopathy, and microcephaly (ATP1A2) [65,66,67]. This evidence concerns the gene KCNB1 and microcephaly.