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Klinefelter syndrome is a genetic disorder that affects males. Klinefelter syndrome occurs when a boy is born with one or more extra X chromosomes. Most males have one Y and one X chromosome. Having extra X chromosomes can cause a male to have some physical traits unusual for males. Many men with an extra X chromosome are not aware that they have it, and they lead normal lives. Klinefelter syndrome occurs in about 1 out of 1,000 males.
Klinefelter syndrome is a condition that occurs in men as a result of an extra X chromosome. The most common symptom is infertility. 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).