Other chromosomal syndromes observed in multiple patients with ID/DD included partial trisomy 9p (duplication at chr9p24), 15q11q13 duplication syndrome, 18q deletion syndrome34, Prader–Willi syndrome, 22q11 deletion syndrome (DiGeorge syndrome), 8p23.1 microdeletion syndrome, 22q11.2 duplication syndrome, and MECP2 duplication syndrome. This evidence concerns the gene MECP2 and Down syndrome.