Klinefelter syndrome is the presence of an extra X chromosome in a male.
47 X-X-Y syndrome
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.
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:
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. This can be seen on dental x-rays.
Klinefelter syndrome also increases your risk of:
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.
Bacino CA, Lee B. Cytogenetics. In:Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbookof Pediatrics.19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 74.
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