Rett syndrome (or Rett's disorder) is a progressive neurological disorder that is classified as a pervasive developmental disorder by the DSM-IV. The symptoms of this disorder are easily confused with those of cerebral palsy. The clinical diagnosis specifies a small head and small hands and feet. Stereotypical repetitive hand movements such as mouthing or wringing of the hands are also included as diagnostic signs. Symptoms of the disease include learning disorders and a total inability to socialize. Girls with Rett syndrome are very prone to seizures and gastrointestinal disorders. They typically have no verbal skills, and about 50% of females are ambulatory. Rett syndrome (symbolized RTT) is X-linked dominant, affecting almost exclusively girls. Development is normal until 6-18 months, when language and motor milestones regress, purposeful hand use is lost and acquired microcephaly is seen. Hand-wringing and sighing are characteristic, and those affected develop autistic behavior.