Klinefelter syndrome, 47, XXY, or XXY syndrome is when people have an extra number of X chromosomes. People who have Klinefelter's Syndrome are often called "XXY Males", or "47, XXY Males". Other males can have Klinefelter's Syndrome as well (for example, mice).ro:Cromozomul X#Sindromul Klinefelter (47,XXY sau 48,XXXY)
Klinefelter syndrome Facts for Kids. Kiddle Encyclopedia.