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Klinefelter syndrome
A genetic condition in which a male is born with an extra copy of the X chromosome
Klinefelter's syndrome isn't inherited, but rather occurs only as a result of a random genetic error after conception.
Males born with Klinefelter's syndrome may have low testosterone and reduced muscle mass, facial hair and body hair. Most males with this condition produce little or no sperm.
Treatment may include testosterone replacement and fertility treatment.