In these 12 patients, we detected 2 SNVs in MEF2C and 2 in SCN2A genes, which are associated with mental retardation, stereotypic movements, epilepsy, and/or cerebral malformations22–24; 2 SNVs in the SYNGAP1 gene, which is associated with mental retardation24,25; a deletion of IQSEC2 and KDM5C genes, which are associated with mental retardation26; a gross deletion in chr15 (chr15:22,833,395-28,567,298), which is associated with Prader-Willi syndrome27; and a duplication in chr14 (14q32.11-q32.33(90949120-107287505)), which is associated with mental retardation and development delay28. This evidence concerns the gene SCN2A and epilepsy.