While Klinefelter syndrome is genetic, in that it involves one (or more) extra X chromosome gene, it is not usually hereditary in the conventional sense. That is, Klinefelter syndrome is not inherited, nor does it "run in families." Klinefelter syndrome is usually the result of a random event that occurs during the formation of reproductive cells (eggs and sperm).

 

Klinefelter syndrome research scientists are not sure what puts a couple at risk for conceiving a child with Klinefelter syndrome. Advanced maternal age increases the risk for the XXY chromosome count, but only slightly. Furthermore, recent Klinefelter syndrome research shows that half the time, the extra chromosome comes from the father.