Loss of function mutations in NSD1 are a major cause of Sotos Syndrome (Kurotaki et al., 2002, 2005) which presents with macrocephaly, pre- and postnatal overgrowth, facial dysmorphism, ID, autistic features, developmental delay, and in some cases seizures (Sotos et al., 1964; Fortin et al., 2021). Here, NSD1 is linked to Global developmental delay.