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Klinefelter syndrome

Klinefelter syndrome is the presence of an extra X chromosome in a male.

Causes

Most people have 46 chromosomes. Chromosomes contain all of your genes and DNA, the building blocks of the body. Two sex chromosomes determine if you become a boy or a girl. Girls normally have two XX chromosomes. Boys normally have an X and a Y chromosome.

Klinefelter syndrome is when a boy is born with at least one extra X chromosome. Usually, this occurs due to one extra X. This would be written as XXY.

Klinefelter syndrome occurs in about 1 out of 500 - 1,000 baby boys. Women who get pregnant after age 35 are slightly more likely to have a boy with this syndrome than younger women.

Symptoms

  • Abnormal body proportions (long legs, short trunk, shoulder equal to hip size)
  • Abnormally large breasts (gynecomastia)
  • Infertility
  • Sexual problems
  • Less than normal amount of pubic, armpit, and facial hair
  • Small, firm testicles
  • Tall height

Exams and Tests

Klinefelter syndrome may first be diagnosed when a man comes to the doctor because of infertility. Infertity is the most common symptom.

The following tests may be performed:

Blood tests will be done to check hormone levels including:

Treatment

Testosterone therapy may be prescribed. This can help:

  • Grow body hair
  • Improve appearance of muscles
  • Improve concentration
  • Improve mood and self esteem
  • Increase energy and sex drive
  • Increase strength

Most men with this syndrome are not able to get a woman pregnant. However, an infertility specialist may be able to help. A special doctor called an endocrinologist may also be helpful.

Support Groups

The American Association for Klinefelter Syndrome Information and Support (AAKSIS) - www.aaksis.org

Possible Complications

Enlarged teeth with a thinning surface is very common in Klinefelter syndrome. This is called taurodontism. This can be seen on dental x-rays.

Klinefelter syndrome also increases your risk of:

When to Contact a Medical Professional

Call for an appointment with your health care provider if your son does not develop secondary sexual characteristics at puberty. This includes facial hair growth and a deepening of the voice.

A genetics counselor can provide information about this condition and direct you to support groups in your area.

Alternative Names

47 X-X-Y syndrome

References

Bacino CA, Lee B. Cytogenetics. In:Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds.Nelson Textbookof Pediatrics.

Update Date 11/2/2012

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