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Spinocerebellar ataxia (SCA) or also known as Spinocerebellar atrophy or Spinocerebellar degeneration, is a progressive, degenerative, genetic disease with multiple types, each of which could be considered a disease in its own right. An estimated 150,000 people in the United States are diagnosed with Spinocerebellar Ataxia. SCAs are the largest group of this hereditary, progressive, degenerative and often fatal neurodegenerative disorder. There is no known effective treatment or cure. Spinocerebellar Ataxia can affect anyone of any age. The disease is caused by either a recessive or dominant gene. In many cases people are not aware that they carry the ataxia gene until they have children who begin to show signs of having the disorder.〔http://www.ninds.nih.gov/disorders/ataxia/ataxia.htm〕 ==Classification== Most of the 60 different types of SCA that have been identified are diagnosed via autopsy, as there is no definitive test that can tell what type of SCA a living individual has or if they have it at all. In 2008, a genetic ataxia blood test developed to test for 12 types of SCA, Friedreich's ataxia, and several others. However, in the SCA group, with so many different types most go with a diagnosis of SCA unidentified or unknown. Usually the diagnosis comes after examination by a neurologist, which includes a physical exam, family history, MRI scanning of the brain and spine, and spinal tap.〔(www.ataxia.org )〕 Many SCAs below fall under the category of polyglutamine diseases, which are caused when a disease-associated protein (i.e., ataxin-1, ataxin-3, etc.) contains a large number of repeats of glutamine residues, termed a polyQ sequence or a "CAG triplet repeat disease" for either the one-letter designation or codon for glutamine respectively. The threshold for symptoms in most forms of SCA is around 35, though for SCA3 it extends beyond 50. Most polyglutamine diseases are dominant due to the interactions of resulting polyQ tail. The first ataxia gene was identified in 1993 and called “Spinocerebellar ataxia type 1" (SCA1); later genes were called SCA2, SCA3, etc. Usually, the "type" number of "SCA" refers to the order in which the gene was found. At this time, there are at least 29 different gene mutations that have been found. The following is a list of some of the many types of ''Spinocerebellar ataxia''. Others include SCA18, SCA20, SCA21, SCA23, SCA26, SCA28, and SCA29. Four X-linked types have been described (, , , ), but only the first of these has so far been tied to a gene (SCAX1). 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「spinocerebellar ataxia」の詳細全文を読む スポンサード リンク
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