by EBSCO Medical Review Board
(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: Accessed November 5, 2020.

Klinefelter syndrome (KS): Overview. National Institute of Child Health and Human Development website. Available at: Accessed November 5, 2020.

Revision Information

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