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Rett syndrome (RTT), originally termed cerebroatrophic hyperammonemia, is a rare genetic postnatal neurological disorder of the grey matter of the brain that almost exclusively affects females but has also been found in male patients. The clinical features include small hands and feet and a deceleration of the rate of head growth (including microcephaly in some). Repetitive stereotyped hand movements, such as wringing and/or repeatedly putting hands into the mouth, are also noted. People with Rett syndrome are prone to gastrointestinal disorders and up to 80% have seizures. They typically have no verbal skills, and about 50% of affected individuals do not walk. Scoliosis, growth failure, and constipation are very common and can be problematic. The signs of this disorder are most easily confused with those of Angelman syndrome, cerebral palsy and autism. Rett syndrome occurs in approximately 1:10,000 live female births in all geographies, and across all races and ethnicities. Rett syndrome was formerly classified as a pervasive developmental disorder by the ''Diagnostic and Statistical Manual of Mental Disorders'' (DSM), together with the autism spectrum disorders and childhood disintegrative disorder. Some argued against this classification because RTT is similar to non-autistic spectrum disorders such as fragile X syndrome, tuberous sclerosis, or Down syndrome where one can see autistic features. It was removed from the DSM-5 in 2013 because it has a known molecular etiology. It was first described by Austrian pediatrician Andreas Rett in 1966. Huda Zoghbi demonstrated in 1999 that Rett syndrome is caused by mutations in the gene MECP2. ==Signs and symptoms== Initial development is normal. Onset occurs between 6 and 18 months of age. During this time there are subtle developmental deviations and early indicators of Rett syndrome. A period of developmental stagnation is followed by developmental regression where language and motor milestones regress, purposeful hand use is lost, and acquired deceleration in the rate of head growth (resulting in microcephaly in some) is seen. Hand stereotypes are typical, and breathing irregularities such as hyperventilation, breathholding, or sighing are seen in many. Early on, autistic-like behavior may be seen. The infant with Rett syndrome often avoids detection until 6–18 months, owing to a relatively normal appearance and some developmental progress. However, closer scrutiny reveals disturbance of the normal spontaneous limb and body movements that are thought to be regulated in the brainstem. The brief period of developmental progress is followed by stagnation and regression of previously acquired skills. During regression, some features are similar to those of autism. It is, hence, easy to mistakenly diagnose Rett syndrome for autism. Signs of Rett syndrome that are similar to autism: * incontinence * screaming fits * inconsolable crying * breath holding, hyperventilation & air swallowing * avoidance of eye contact * lack of social/emotional reciprocity * markedly impaired use of nonverbal behaviors to regulate social interaction * loss of speech * sensory problems Signs of Rett syndrome that are also present in cerebral palsy (regression of the type seen in Rett syndrome would be unusual in cerebral palsy; this confusion could rarely be made): * possible short stature, sometimes with unusual body proportions because of difficulty walking or malnutrition caused by difficulty swallowing * hypotonia * delayed or absent ability to walk * gait/movement difficulties * ataxia * microcephaly in some - abnormally small head, poor head growth * gastrointestinal problems * some forms of spasticity * chorea - spasmodic movements of hand or facial muscles * dystonia * bruxism – grinding of teeth Signs may stabilize for many decades, particularly for interaction and cognitive function such as making choices. Asocial behavior may change to highly social behavior. Motor functions may slow as rigidity and dystonia appear. Seizures may be problematic, with a wide range of severity. Scoliosis occurs in most, and may require corrective surgery. Those who remain ambulatory tend to have less progression of scoliosis. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rett syndrome」の詳細全文を読む スポンサード リンク
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