Rett syndrome is a X-linked neurodevelopmental disorder that affects 1 in 10,000 females. It presents itself clinically with developmental regression at 6-18 months of age, with loss of acquired language and motor skills, leading to a complex lifelong syndrome characterised by intellectual disability; behavioural and neuropsychiatric disturbances; social withdrawal; hand stereotypies; epilepsy; autonomic dysfunction causing breathing irregularities and cardiac arrhythmias; muscle tone abnormalities leading to orthopaedic deformities such as scoliosis; and motor incoordination that causes gait disturbance and feeding difficulties which, along with a number of gastrointestinal problems, leads to growth failure and nutritional deficiencies. This book discusses symptoms, treatment and prognosis of Rett Syndrome, as well as other related communication disorders.