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by EBSCO Medical Review Board

Klinefelter Syndrome

(47 XXY Syndrome; KS)


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


The doctor will ask 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.


There is no cure. The goal is to manage symptoms. Choices are:
  • Testosterone therapy to raise low levels of this hormone
  • Speech and language therapy
  • Special education services
  • Mental health counseling


There are no known guidelines to prevent KS.


The Association for X and Y Chromosome Variations
National Institute of Child Health and Human Development


Canadian Psychiatric Association
Canadian Psychological Association


Groth KA, Skakkebæk A, et al. Clinical review: Klinefelter syndrome--a clinical update. J Clin Endocrinol Metab. 2013 Jan;98(1):20-30.
Klinefelter syndrome. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/klinefelter-syndrome. Accessed November 5, 2020.
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 November 5, 2020.

Revision Information

  • Reviewer: EBSCO Medical Review Board Kari Kassir, MD
  • Review Date: 09/2020
  • Update Date: 05/11/2021