STAG1 and Global developmental delay: The heterozygous intragenic deletions within the STAG1 gene, de novo heterozygous missense and frameshift STAG1 gene variants in 17 unrelated patients with similar phenotypes (intellectual disability/developmental delay, growth retardation, feeding difficulties, facial dysmorphism, epilepsy, autistic features) were first reported by Lehalle et al. who considered the STAG1 gene could be a novel gene responsible for non-specific syndromic intellectual disability (1).