Klinefelter syndrome.

Klinefelter syndrome, affecting males, is a collection of characteristics that occurs as a result of two or more X chromosomes. The syndrome was named after Harry Klinefelter, an American endocrinologist, and is common - occurring in all races. It is thought that one male in every 500 live births is affected and the incidence is rising. However, this may be due to increasing awareness, reflective of the sophistication of the methods to diagnose.