GRIA2 is implicated in ID [65,66,67] and ASD [68], and recently, 20 heterozygous de novo GRIA2 variants were identified in 28 individuals with ID, ASD, and Rett syndrome-like features as well as seizures or DEE, suggesting that a defective GluA2 leads to NDD [69]. This evidence concerns the gene GRIA2 and atypical Rett syndrome.