[Genetic basis for Rett disease]

Current knowledge concerning the genetic background of Rett syndrome (RS) is reviewed. RS is a progressive neurological disorder causing severe mental retardation which appears to be limited to the female sex. The genetic defect responsible for the illness is not known and several different causative mechanisms i.e. X-linked dominant mutation, the two step mutation theory, mitochondrial DNA mutation, gonadal mosaicism, alternation in the X inactivation process, uniparental disomy of the X chromosome are reviewed.