Klinefelter syndrome 47,XXY

What is Klinefelter syndrome or 47,XXY?:

Klinefelter syndrome is a rare genetic condition in which a man has an extra X chromosome. Some conditions associated with Klinefelter are hypothyroidism, infertility, testicular cancer, and an increased risk of male breast cancer.

What are some symptoms?:

  • testosterone deficiency
  • enlarged breasts (gynecomastia)
  • sparse facial and body hair
  • small hard testes
  • inability to produce sperm (infertility)

Chromosomes and Klinefelter syndrome, 47XXY:

People typically have two sex chromosomes in each cell. Females have two X chromosomes, and males have one X and one Y. Males with Klinefelter syndrome most often have a single extra copy of the X chromosome, for a total of 47 chromosomes per cell; this is referred to as (47,XXY.) Some men with Klinefelter syndrome have the extra X chromosome in only some of their cells; this is called "mosaic 46,XY/47,XXY." Extra copies of the X chromosome interfere with male sexual development and testicular functioning, thus explaining some of the conditions outlined above.

Cause of Klinefelter syndrome:

Klinefelter syndrome is not an inherited condition but occurs at random. It's usually the result of an error that occurs during cell division during the formation of egg or sperm cells. For example, an egg or sperm cell may have an extra copy of the X chromosome as a result of improper cell division. If one of these cells is involved in conception, the result is a child with an extra X chromosome in each of the body's cells. When the error in cell division occurs early in fetal development (rather than before fertilization) the result is a mosaic, meaning that not every cell in the body is affected.

Impact on a Male:

Since 47XXY may not be present in every cell in the body, each case is different. Not all symptoms may appear, and many cases go undiscovered. The most common concerns are:

  • male breast cancer
  • infertility
  • osteoporosis
  • depression
  • diabetes
  • thyroid problems
  • leg ulcers
  • dental problems


Testosterone can be given therapeutically, to assist body development as a male progresses into maturity. If testosterone is given for Klinefelter syndrome, it must be continued consistently for a lifetime.

Hormonal therapy will not improve fertility, but testicular sperm extraction and in vitro fertilization may help result in a pregnancy.

If a mature male has some distress about sexual identity or sexual disfunction, professional counseling can help.

Relationship to Gynecomastia and Male Breast Cancer:

Klinefelter syndrome is associated with an increased risk of developing male breast cancer. Gynecomastia (prominent breasts in a male) is one symptom of Klinefelter syndrome. Having extra breast tissue increases the risk of developing breast cancer.

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Article Sources

  • American Association for Klinefelter Syndrome Information & Support. A Guide to Klinefelter Syndrome (PDF document). Last revised date: 2005. A Guide to Klinefelter Syndrome
  • National Institutes of Health. What is Klinefelter Syndrome? Understanding Klinefelter Syndrome. Last revised date: 15 August 2006. What is Klinefelter Syndrome?
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