GRIN2B and Intellectual disability: DD and/or intellectual disability (ID) can develop in all disorders, while autistic features are described in 6/27 (22%: CDKL5, KCNQ2, GRIN2B, SCN2A, STXBP1, and VAMP2), regression in 7/27 (26%: AP3B2, CACNA1E, CDKL5, FHF1, GRIN2B, SCN8A, and STXBP1), and stagnation in 2 (7%: GABRB3, GNAO1).