P370: Characteristic neural tube defects and overlap in OEIS complex and lumbar syndrome

families had children with ASD with discordant cognitive impairment.De novo variants were identified in the proband with cognitive impairment (DDX3X, n=1; FBXW7, n=1).Sanger sequencing confirmed these variants were absent in the comparator sibling with ASD without cognitive impairment.Definitive diagnoses resulted in one or more changes in management in 50% (5/10) including eligibility for targeted therapy (n=1), tumor surveillance (n=1), specialist referral (n=3).Four children (12%) had additional clinically significant findings unrelated to ASD.Conclusion: Genome sequencing is effective to identify both common and more rare genomic disorders in young children with ASD and cognitive delays.cGS could be considered as a first-line genetic testing, particularly in children with complex phenotypes.This study adds to the growing literature supporting genome-wide sequencing in children with neurodevelopmental disorders.