Klinefelter syndrome is a genetic disorder that affects roughly one out of every 1,000 males. It occurs when a boy is born with one or more extra X chromosomes. Normally, boys have one Y chromosome and one X chromosome. Though often not diagnosed until adulthood, the presence an extra X chromosome can cause unusual physical traits.

What causes Klinefelter syndrome?

The existence of an extra chromosome in a male typically happens when the genetic material in the egg splits unevenly during conception. Klinefelter syndrome stems from a random genetic event, and it is not passed down through families.

What are the symptoms?

Symptoms of Klinefelter syndrome vary, though many men who have it do not have obvious symptoms. However, for others, the condition can have a noticeable effect on growth or appearance such as sparse body hair, enlarged breast tissue, increased abdominal fat and reduced muscle mass. Some boys with Klinefelter syndrome may have language and learning problems. Adult males tend to be infertile.

When/how is it diagnosed?

Klinefelter syndrome usually is not diagnosed until the time of puberty when the testicles fail to grow normally. If you’re concerned your son or you may have Klinefelter syndrome, consult a physician. He or she will do a thorough physical exam and a chromosome test (called a karyotype) to determine if the condition is present.