Both of these patients carried the same missense variant in STXBP1 gene: (NM_003165), c.1216C > T; p.R406C, this variant was reported as a pathogenic variant in a case of Ohtahara syndrome with profound ID31, which matches our result and support the findings of previously reported studies that mutation in STXBP1 is extensively associated with severe early-onset epileptic encephalopathies including Ohtahara syndrome, West syndrome and other epileptic phenotypes with moderate to severe ID32, 33, 34, 35. This evidence concerns the gene STXBP1 and early-infantile DEE.