Rett syndrome was first described in 1966 by the Austrian doctor, Andreas Rett. It is a complex neurological disorder, genetic in origin. It affects mainly girls. A few boys also have the condition.

At least one in every 10,000 females born has Rett syndrome. It is believed to be the second most common cause of severe and profound learning disability in girls.

A large proportion of people who have Rett syndrome have a mutation, or fault, on the MECP2 gene on the X chromosome. Rett syndrome is not usually passed down to the child from their parents.

It could occur in any family at any time. Something goes wrong with the genetic makeup of the cells which become the baby.