MECP2 and neurodevelopmental disorder: Rett syndrome is a severe neurodevelopmental disorder, occurring mainly in females and usually associated with a mutation of the methyl-CpG-binding protein 2 (MECP2) gene.1 It occurs rarely2 with a wide phenotypic spectrum in part explained by the specific MECP2 mutation.3 Following apparently normal early development, there is loss of communication and hand function with the development of intense midline hand stereotypies.