Some genetic disorders consistently linked to ASD, including Angelman syndrome, fragile X syndrome, tuberous sclerosis, Rett syndrome, and other MECP2-related disorders, Smith-Lemli-Opitz syndrome, phenylketonuria, Cohen syndrome, Smith-Magenis syndrome, Sanfilippo syndrome, adenylosuccinate lyase deficiency, Down syndrome, 22q13 deletion syndrome (Cohen et al., 2005; Bukelis et al., 2007). Here, MECP2 is linked to Down syndrome.