TSC2 and Down syndrome: There are several single‐gene mutation syndrome disorders that are associated with an increased risk of developing ASD including Fragile X (FMR1), Rett Syndrome (MECP2), Tuberous sclerosis (either TSC1 or TSC2), Timothy syndrome (CACNA1C), Angelman syndrome (UBE3A), and Cowden syndrome (PTEN) (Belmonte & Bourgeron, 2006; Butler et al., 2005; Nagarajan et al., 2008; Splawski et al., 2004; Wiznitzer, 2004).