Klinefelter Syndrome

(47 XXY Syndrome; KS)


Klinefelter syndrome (KS) occurs in some men who have more than one X chromosome (XXY).
Klinefelter's Syndrome
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Males usually inherit a single X chromosome from their mother and a single Y chromosome from their father. Males with KS get at least one extra X chromosome.

Risk Factors

Women over age 35 may have a slightly increased chance of having a child with KS. There are no other known risk factors for this disorder.


Most men with KS do not have symptoms. When KS does develop, it usually goes undetected until puberty or sometimes much later.Babies may have lower birthweight, or slower muscle and motor development.Children or adults may have:
  • Social and learning disabilities
  • Enlarged breasts
  • Inability to produce sperm
  • Small firm testes
  • Small penis
  • Abnormal body proportions, such as long legs or short trunk
  • Tallness with extra long arms and legs
  • Personality impairment
  • Attention deficit hyperactivity disorder (ADHD)
  • Speech and language problems—Children with KS often learn to speak later than other children do. They may have a difficult time reading and writing.
  • Normal to borderline IQ
  • Lack of facial and body hair
  • Diminished sex drive or sexual dysfunction
Men with KS have an increased risk of:

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