Rett syndrome (RS) is a neurodevelopmental disorder that occurs almost exclusively in females and has a typically degenerative course. It is related to various mutations on the MECP2 gene, which codes for methyl-CpG binding protein-2 (MECP2). Recent studies suggest that MECP2 is expressed in neurons and glial cells and that it will someday be possible to reverse the disorder even after birth when behavioural symptoms occur.