The prime pathogenesis of Rett syndrome is known to be various genetic mutations in methyl CpG-binding protein 2 gene (MeCP2) on the X chromosome, cyclin-dependent kinase-like 5 (CDKL5), forkhead box G1 (FOXG1), WD repeat domain 45 (WDR45) or syntaxin binding protein 1 (STXBP1) [181,182]. The gene discussed is FOXG1; the disease is atypical Rett syndrome.