Klinefelter syndrome is the presence of an extra X chromosome in a male.
47 X-X-Y syndrome
Causes, incidence, and risk factors:
Humans have 46 chromosomes. Chromosomes contain all of your genes and DNA, the building blocks of the body. The two sex chromosomes determine if you become a boy or a girl. Females normally have two XX chromosomes. Males normally have an X and a Y chromosome.
Klinefelter syndrome is one of a group of sex chromosome problems. It results in males who have 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 newborn boys. Women who get pregnant after age 35 are slightly more likely to have a boy with this syndrome than younger women.
- Abnormal body proportions (long legs, short trunk, shoulder equal to hip size)
- Abnormally large breasts (gynecomastia )
- Sexual problems
- Less than normal amount of pubic, armpit, and facial hair
- Small, firm testicles
- Tall height
Signs 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:
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.
The American Association for Klinefelter Syndrome Information and Support (AAKSIS) - www.aaksis.org
Enlarged teeth with a thinning surface is very common in Klinefelter syndrome. This is called taurodontism. It can be diagnosed by dental x-rays.
Klinefelter syndrome also increases your risk of:
Calling your health care provider:
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.
|Review Date: 11/1/2010|
Reviewed By: Chad Haldeman-Englert, MD, Wake Forest University School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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