A condition in which a person has one Y-chromosome and two (or more) X-chromosomes, usually characterized by low testosterone levels, small testicles, tall stature and long limbs, sparse body hair, and infertility.
A genetic condition in which a male is born with two X chromosome.
The Official Patient's Sourcebook on Klinefelter Syndrome.
By mid-puberty, boys with Klinefelter syndrome have low levels of testosterone, resulting in small testicles and the inability to make sperm.
Approximately 3% of the infertile male population have Klinefelter syndrome.
Most commonly, a male with Klinefelter syndrome will be born with 47 chromosomes in each cell, rather than the normal number of 46.
Because people with Klinefelter syndrome have a Y chromosome, they are all male.