A wide range of neurodevelopmental disorders are associated with MECP2 mutations/altered expression; including Rett Syndrome (RTT; loss-of-function), autism spectrum disorder (ASD; reduced expression), fetal alcohol spectrum disorders (FASD; altered expression), MECP2 duplication syndrome (MDS; gain-of-function), and severe neonatal encephalopathy [12,13]. The gene discussed is MECP2; the disease is atypical Rett syndrome.