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Klinefelter syndrome or Klinefelter's syndrome (KS) () also known as 47,XXY or XXY, is the set of symptoms that result from two or more X chromosome in males. The primary feature is sterility.〔 Often symptoms may be subtle and many people do not realize they are affected. Sometimes symptoms are more prominent and may include weaker muscles, greater height, poor coordination, less body hair, smaller genitals, breast growth, and less interest in sex.〔 Often it is only at puberty that these symptoms are noticed. Intelligence is usually normal; however, reading difficulties and problems with speech are more common. Symptoms are typically more severe if three or more X chromosomes are present. Klinefelter syndrome usually occurs randomly. An older mother might increase the risk slightly. The condition is not inherited from one's parents.〔 The underlying mechanisms involves at least one extra X chromosome in addition to a Y chromosome such that there is a total of 47 or more chromosomes rather than usual 46. KS is diagnosed by the genetic test known as a karyotype.〔 While there is no cure a number of treatments may help.〔 Physical therapy, speech and language therapy, counselling, and adjustments of teaching methods may be useful. Testosterone replacement may be used in those who have significantly low levels. Enlarged breasts may be removed by surgery. About half of males affected with the help of assisted reproductive technology have a chance of having children; however, this is expensive and carries risks. The condition has a nearly normal life expectancy. Klinefelter syndrome is one of the most common chromosomal disorders, occurring in 1:500 to 1:1000 live male births. It is named after Harry Klinefelter who identified the condition in the 1940s. 1956 saw the identification of the extra X chromosome. Mice also can have the XXY syndrome, making them a useful research model. ==Signs and symptoms== While it is possible to characterise XXY males based on physical characteristics, substantial variation in physical and developmental traits mean the only reliable method of positive or negative identification is karyotype testing. 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「Klinefelter syndrome」の詳細全文を読む スポンサード リンク
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