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Definition
By Mayo Clinic staffKlinefelter syndrome is one of the most common genetic conditions affecting males. It usually occurs as the result of an extra copy of the X chromosome in each cell. Klinefelter syndrome affects between one in 500 and one in 1,000 males.
The effects of Klinefelter syndrome vary from person to person. Because the condition can affect testicular growth, boys born with Klinefelter syndrome have low levels of the sex hormone testosterone. This can lead to reduced muscle growth, reduced body and facial hair, and enlarged breast tissue (gynecomastia). In some cases Klinefelter syndrome can cause learning and social problems during childhood and adolescence.
In most cases, Klinefelter syndrome isn't diagnosed until adulthood. But in cases where Klinefelter syndrome is diagnosed with a genetic test before birth or during childhood, treatment can help prevent or treat problems caused by the condition. Most men with Klinefelter syndrome are unable to father children (infertile), though new procedures make it a possibility for some men.
- Klinefelter syndrome. National Institutes of Health. http://www.nichd.nih.gov/health/topics/klinefelter_syndrome.cfm. Accessed Feb. 19, 2008.
- Klinefelter syndrome. Madison's Foundation. http://www.madisonsfoundation.org/index.php/component/option,com_mpower/diseaseID,195/. Accessed Feb. 19, 2008.
- Lanfranko F, et al. Klinefelter's syndrome. The Lancet. 2004;364(9430):273-283
- Bojesen A, et al. Klinefelter syndrome in clinical practice. Nature Clinical Practice Urology. 2007;4(4):192-193.
- Klinefelter syndrome. U.S. National Library of Medicine. http://ghr.nlm.nih.gov/condition=klinefeltersyndrome. Accessed Feb. 26, 2008.
- Klinefelter (XXY) syndrome. California Department of Developmental Services. http://www.ddhealthinfo.org/coursebuilder/?id=25. Accessed Feb. 19, 2008.
