Klinefelter syndrome (KS) happens in men who have more than one X chromosome (XXY).
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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.
There are no known risk factors for KS.
Symptoms may not be found until puberty or later.
Children may have problems with:
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.
Last reviewed September 2020 by EBSCO Medical Review Board Kari Kassir, MD Last Updated: 5/11/2021