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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Causes    TOP

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    TOP

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.

Symptoms    TOP

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:

Diagnosis    TOP

A test called a karyotype is used to diagnose KS. In the case of KS, there are usually 47 chromosomes rather than the normal 46.

Many men with XXY do not know they have the condition. Diagnosis of KS may be found incidentally. For example:

Treatment    TOP

Treatment of KS includes:


The main treatment is testosterone . When boys with KS are 10-12 years old, their hormone levels are checked yearly. If testosterone levels are low, then treatment may be helpful. Men diagnosed may also benefit from taking the hormone. However, testosterone cannot reverse infertility.

The benefits of testosterone include:

  • Increased strength
  • More muscular, male appearance
  • Growth of facial and body hair
  • Better self-esteem
  • Modulation of mood
  • Increased energy
  • Increased ability to concentrate
  • Greater sex drive
  • Improved bone density

Speech and Language Therapy

This therapy should begin in early childhood to avoid social and school learning problems. Treatment may involve:

  • Speech therapy
  • Special education services
  • Extra support and help with learning from parents and teachers
  • Social skills training and psychological counseling

Prevention    TOP

There are no current guidelines to prevent KS. If you are pregnant, talk to your doctor about prenatal care and screening tests.


Klinefelter Syndrome and Associates
National Institute of Child Health and Human Development


Canadian Psychiatric Association
Canadian Psychological Association


Klinefelter syndrome. EBSCO DynaMed website. Available at:
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Updated March 17, 2015. Accessed June 18, 2015.
Tell me about 47, XXY. Klinefelter Syndrome and Associates website. Available at:
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Accessed June 18, 2015.
Klinefelter syndrome (KS): Overview. National Institute of Child Health and Human Development website. Available at:
...(Click grey area to select URL)
Updated November 15, 2013. Accessed June 18, 2015.
Last reviewed June 2015 by Michael Woods, MD
Last Updated: 5/11/2013

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