A rare genetic neurodevelopmental disorder characterized by global developmental delay, severe intellectual disability and absence of expressive language. Muscular hypotonia, seizures, autistic behavior and stereotypic movements are common. The disorder is caused by homozygous or compound heterozygous intragenic deletions or truncating variants in the NRXN1 gene (2p16.3). NRXN1 belongs to the evolutionarily conserved family of neurexins, presynaptic transmembrane proteins and has an important role in synaptic function. Inheritance is autosomal recessive. [from SNOMEDCT_US]