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Klinefelter Syndrome

(47 XXY Syndrome; KS)


Klinefelter syndrome (KS) happens in men who have more than one X chromosome (XXY).


Males have a single X chromosome from their mother and a single Y one from their father. Males with KS get at least one extra X from either parent.

Risk Factors

There are no known risk factors for KS.


Symptoms may not be found until puberty or later.

Children may have problems with:

  • Speech
  • Learning
  • Behavior

Teens may have:

  • Delayed puberty
  • Enlarged breasts

Adults may have:

  • Small, firm testes
  • Small penis
  • A poor sex drive or sexual problems
  • Lack of facial and body hair
  • Breast pain
  • Hot flashes, sweating


You will be asked about your symptoms and health history. A physical exam will be done.

KS is diagnosed with a genetic test. Blood tests may also be done.


KS is treated with:


Boys with KS have their hormone levels checked every year. If testosterone levels are low, then testosterone therapy may help. It may also help adults.

Speech and Language Therapy

This therapy should start early to avoid social and school problems. It may involve:

  • Speech therapy
  • Special services at school
  • Extra support and help with learning from parents and teachers
  • Social skills training and mental health counseling


KS can’t be prevented. If you are having fertility treatment, ask about genetic testing.


The Association for X and Y Chromosome Variations

National Institute of Child Health and Human Development


Canadian Psychiatric Association

Canadian Psychological Association


Klinefelter syndrome. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T116877/Klinefelter-syndrome. Updated March 6, 2017. Accessed July 6, 2018.

About 47, XXY (Klinefelter syndrome). Klinefelter Syndrome and Associates website. Available at: The Association for X and Y Chromosome Variations. Accessed July 6, 2018.

Klinefelter syndrome (KS): Overview. National Institute of Child Health and Human Development website. Available at: http://www.nichd.nih.gov/health/topics/klinefelter/Pages/default.aspx. Accessed July 6, 2018.

Last reviewed May 2018 by Kari Kassir, MD  Last Updated: 7/6/2018