Although still commonly used, the term "Klinefelter's syndrome" is slowly being replaced by the term XXY males to describe males having the extra X chromosome. It is the most common chromosomal abnormality in males, resulting in deficient testicular function and occurring in 1 out of 500 live births. Gynecomastia and various degrees of testosterone deficiency are usually noted.

	Male Breast Cancer The Condition "...Men with Klinefelter's syndrome have an increased risk of developing breast cancer, as do men who take estrogens or estrogen-like compounds..."

Last updated: Oct 08, 2008