Klinefelter’s syndrome is one of the most common sex chromosome disorder among males, affecting up to 1 in 500 births. A completely random occurrence, the condition arises when a boy inherits an extra X chromosome from one of his parents. Instead of the typical XY, boys with Klinefelter’s syndrome have an XXY set.

The condition was first identified in 1942 by the physician Henry Klinefelter of Massachusetts General Hospital in Boston. He published a report on nine men with enlarged breasts, small testes, sparse facial and body hair, and an inability to produce sperm. These symptoms are the result of the low testosterone levels that are associated with Klinefelter’s syndrome.

Most cases of Klinefelter’s aren’t diagnosed until later in life. Babies show few symptoms, although they tend to take longer to sit up and crawl than other infants. During puberty, they may have smaller testicles, less body hair, and lower energy levels than other boys their age. Men with Klinefelter’s syndrome often are unable to father children, because they don’t produce a normal amount of sperm. They also have an increased risk of varicose veins, osteoporosis, and abdominal fat.

To diagnose the disorder, physicians perform hormone testing and a chromosome analysis, or karyotype. Doctors often recommend testosterone treatment during puberty and, for some men, surgical removal of excess breast tissue.

ADDITIONAL FACTS

  1. Some men with Klinefelter’s syndrome who wish to father children can opt for a treatment known as testicular sperm extraction, in which sperm are removed from the testicles and injected directly into the egg.
  2. People affected by the condition have a 25 percent chance of having mental retardation.