Hypomorphic mutations of OGT are implicated in an X-linked intellectual disability syndrome (Pravata et al., 2020a; Pravata et al., 2019; Selvan et al., 2018; Willems et al., 2017; Vaidyanathan et al., 2017), a severe neurodevelopmental disorder now termed OGT-associated Congenital Disorder of Glycosylation (OGT-CDG) (Pravata et al., 2020b). Here, OGT is linked to X-linked non-syndromic intellectual disability.