MECP2 and Rett syndrome: MECP2 mutations that cause classic RTT in females typically lead to neonatal encephalopathy and death in the first year of life in male and some of these mutations have been reported in males with classic RTT and a normal karyotype (Chahrour and Zoghbi, 2007), suggesting that MECP2 mutations in males lead to more severe effects due to absence of normal MECP2 and MECP2 mutations in females exhibit moderate phenotypes compared with the case of males.