Rett syndrome: prevalence among Chinese and a comparison of MECP2 mutations of classic Rett syndrome with other neurodevelopmental disorders.

Rett syndrome is an X-linked dominant neurodevelopmental disorder. Mutation of the methyl-CpG-binding protein 2 gene (MECP2) is present in up to 96% of patients with Rett syndrome. Eight mutations represent the hotspot of MECP2 mutations (R106W, R133C, T158M, R168X, R255X, R270X, R294X, and R306C) in patients with classic Rett syndrome. The prevalence and survival rate of Rett syndrome among Chinese women was investigated. The 8 hotspot mutations and the A140V mutation were also studied in 4 cohorts of Chinese children (n = 144) actively followed up in our university neurodevelopmental center with classic Rett syndrome (n = 5), autism spectrum disorder (n = 94), epileptic encephalopathy of unknown cause (n = 22), and nonsyndromal mental retardation (n = 23). The prevalence of Rett syndrome among female Chinese younger than 35 years in Hong Kong West is 0.57 (95% confidence interval, 0.15-0.98) per 10 000. Survival is 100.0% at 10 years and 87.5% at 25 years. Three hotspot mutations (R106W, R255X, and R306C) were found in 3 girls with classic Rett syndrome. No hotspot MECP2 mutations were found in the other 3 cohorts. Screening of MECP2 mutations is not worthwhile in Chinese children with pure cognitive, autistic, or unexplained epileptic disorders without other signs of Rett syndrome. In the early stage of developmental arrest before developmental regression, MECP2 screening might be useful for girls with unexplained epileptic encephalopathy before full-blown classic Rett syndrome is evident.