A Brief Review of the Scientific Background

In 1942 Dr Harry Klinefelter, a Baltimore endocrinologist and his co-workers, who were working at the Massachusetts General Hospital, USA, published a study. It was about nine men who had enlarged breasts, sparse facial and body hair and 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 47XXY.

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. All are known as Klinefelter’s Syndrome.

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