Klinefelter syndrome

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Klinefelter syndrome

Definition:

Klinefelter syndrome is a condition that occurs in men as a result of an extra X chromosome. The most common symptom is infertility.

Alternative Names:
47 X-X-Y syndrome
Causes, incidence, and risk factors:

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Humans have 46 chromosomes, which contain all of a person?s genes and DNA. Two of these chromosomes, the sex chromosomes, determine a person?s gender. Both of the sex chromosomes in females are called X chromosomes. (This is written as XX.) Males have an X and a Y chromosome (written as XY). The two sex chromosomes help a person develop fertility and the sexual characteristics of their gender.

Klinefelter syndrome results in males who have at least one extra X chromosome. Usually, this occurs as a result of one extra X (written as XXY).

Klinefelter syndrome is found in about 1 out of every 500-1,000 newborn males. Women who have pregnancies after age 35 are slightly more likely to have a boy with this syndrome than younger women.