Monogenic disorders accounted for in ASD include Fragile X Syndrome (FMR1), Tuberous Sclerosis (TSC1, TSC2), Angelman and Prader-Willi Syndromes (15q11–q13 deletion/UBE3A and GABRB3 deletion), Rett Syndrome (MECP2), Phelan-McDermid syndrome (PMS; 22q13.3 deletion/SHANK3 mutation), Smith-Lemli-Opitz Syndrome (DHCR7), Neurofibromatosis (NF1), Timothy Syndrome (CACNA1C), et cetera (Muhle et al., 2004; Moss and Howlin, 2009; Geschwind, 2011; Ramaswami and Geschwind, 2018). This evidence concerns the gene MECP2 and atypical Rett syndrome.