Understanding Klinefelter Syndrome
WHAT IS KLINEFELTER SYNDROME? In 1942, Dr. Harry Klinefelter and his coworkers at the Massachusetts General Hospital in Boston published a report about nine 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, XXY instead of the usual male arrangement, 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, sponsored by the National Institute of Child Health and Human Development (NICHD), 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.
