All information on this site is correct to the best of our knowledge, however the KSA (UK) recommends that you verify all facts before acting upon them.  Medical treatment and advice should always be confirmed by your GP, consultant or family doctor.

Scientific Background

In 1942 Dr Harry Klinefelter, a Baltimore endocrinologist and his co-workers who were working at the Massachusetts General Hospital, published a study about nine men who had enlarged breasts, sparse facial & body hair & small, firm, infertile testes.

 

By the late 1950s other researchers discovered that subjects with Klinefelter's Syndrome had an extra sex chromosome giving them a karyotype of XXY .(XXXY and XXXXY are also considered to be KS) While women usually inherit two X chromosomes - one from each parent, men inherit an X from their mothers and a Y from their fathers. However occasionally an egg with two Xs (XX) or a sperm with both an X and a Y (XY) can occur resulting in two chances of producing an XXY person. Either an XY sperm fertilises an X egg or a Y sperm fertilises an XX egg.

 

There are other less common variations; for example 48XXXY or 49XXXXY. There is also a mosaic type where some of the body cells do not have the extra chromosome(s).