Rett syndrome is a rare genetic disease that disrupts the development and maturation of the brain. It manifests itself in babies and toddlers, almost exclusively among girls.

A child with Rett syndrome demonstrates normal development early in life. The first symptoms appear between 6 and 18 months. Children with the disease gradually have problems with movements, coordination and communication that affect their ability to speak, walk and use their hands. We then speak of polyhandicap.

A new classification for pervasive developmental disorders (PDD).

Although Rett syndrome is a genetic disease, it is part of pervasive developmental disorders (PDD). In the next edition (forthcoming 2013) of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), the American Psychiatric Association (APA) proposes a new classification for PDD. The different forms of autism will be grouped into a single category called “Autism Spectrum Disorders”. Rett syndrome will therefore be considered a rare genetic disease that is completely separate.