MECP2 and attention deficit-hyperactivity disorder: The duplication in the Xq27.3q28 region has been linked to “Xq28 Methyl-CpG-binding protein 2 duplication syndrome” and “Xq28 duplication syndrome.” The Xq28 duplication syndrome is an X-linked disorder associated with intellectual disability, cognitive impairment, attention-deficit hyperactivity disorder, behavioral abnormalities, recurrent infections, obesity, and infantile hypotonia in males.