Klinefelter syndrome


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Definition

By Mayo Clinic staff

Klinefelter syndrome is a genetic condition that results when a boy is born with an extra copy of the X chromosome. Klinefelter syndrome is a common genetic condition affecting males.

Klinefelter syndrome adversely affects testicular growth, and this can result in smaller than normal testicles. This can lead to lower production of the sex hormone testosterone. Klinefelter syndrome may also cause reduced muscle mass, reduced body and facial hair, and enlarged breast tissue. The effects of Klinefelter syndrome vary, and not everyone with it develops these signs and symptoms.

Klinefelter syndrome often isn't diagnosed until adulthood. Most men with Klinefelter syndrome produce little or no sperm. But assisted reproductive procedures may make it possible for some men with Klinefelter syndrome to father children.

Symptoms
References
  1. Kliegman RM, et al. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.mdconsult.com/das/book/body/208746819-6/0/1608/0.html. Accessed April 29, 2013.
  2. Melmed S, et al. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.mdconsult.com/das/book/body/191205553-3/0/1555/0.html#. Accessed April 29, 2013.
  3. Wikstrom AM, et al. Klinefelter syndrome. Best Practice & Research Clinical Endocrinology & Metabolism. 2011;25:239.
  4. Sokol RZ. It's not all about the testes: Medical issues in Klinefelter patients. Fertility and Sterility. 2012;98:261.
  5. Klinefelter syndrome. Genetics Home Reference. http://ghr.nlm.nih.gov/condition/klinefelter-syndrome. Accessed April 29, 2013.
  6. Klinefelter syndrome. National Institute of Child Health and Development. http://www.nichd.nih.gov/health/topics/klinefelter/conditioninfo/Pages/Default.aspx. Accessed April 29, 2013.
  7. Learning about Klinefelter syndrome. National Human Genome Research Institute. http://www.genome.gov/19519068. Accessed April 29, 2013.
  8. Nippoldt TB (expert opinion). Mayo Clinic, Rochester, Minn. May 2, 2013.
DS01057 June 25, 2013

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