Genetics Home > History of Klinefelter Syndrome
The history of Klinefelter syndrome began in 1942, when the symptoms were first identified. By the late 1950s, the cause of Klinefelter syndrome was discovered. The history of Klinefelter syndrome has shown that it is one of the most common genetic abnormalities known, although not all males with the extra X chromosome will show signs of Klinefelter syndrome.
In 1942, Dr. Harry Klinefelter and his coworkers at the Massachusetts General Hospital in Boston published a report about 9 men who had enlarged breasts, sparse facial and body hair, small testes, and an inability to produce sperm.
By the late 1950s, researchers discovered that men with Klinefelter syndrome, as this group of symptoms came to be called, had an extra sex chromosome, resulting in a chromosomal arrangement of XXY; the usual male arrangement is XY.
In the early 1970s, researchers around the world sought to identify males having the extra chromosome by screening large numbers of newborn babies. One of the largest of these studies checked the chromosomes of more than 40,000 infants.
Based on these studies, the XXY chromosome arrangement appears to be one of the most common genetic abnormalities known, occurring as frequently as 1 in 500 to 1 in 1,000 male births.
While many men have an extra X chromosome, not a lot actually have Klinefelter syndrome symptoms. Many men live out their lives without ever suspecting that they have an additional chromosome.