Klinefelter
Klinefelter is a genetic condition caused when males are born with two X chromosomes and one Y chromosome. Males normally have an X chromosome and a Y chromosome, however, if they are born with Klinefelter Syndrome they have XXY in their genetic make-up. Affected individuals typically have small testes that do not produce as much testosterone as usual, a shortage of testosterone that can lead to delayed or incomplete puberty, reduced facial and body hair, and infertility. Some affected individuals also have genital differences including undescended testes, the opening of the urethra on the underside of the penis, or an unusually small penis. About one of every 500 men are born with Klinefelter Syndrome.