• If a comprehensive history and exam are indicative of a specific syndrome or disorder, proceed with specific testing in patients with ASD and/or ID/GDD. • In all individuals with ASD and ID/GDD without specific findings, consider CMA and FMR1 CGG repeat analysis. • In females with ASD and/or ID/GDD without specific findings, consider MECP2 testing. • In males with ID/GDD without specific findings, consider an X-linked ID panel (XLID). • If an etiology is not identified, consider a referral to genetics for additional work-up including possible ES. This evidence concerns the gene MECP2 and Global developmental delay.