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