Klinefelter syndrome is a genetic disorder that affects males.
Normally, males have one X and one Y chromosome; males with
Klinefelter syndrome have at least two X chromosomes and, in
rare cases, as many as three or four. Symptoms, when present,
vary from one male to another depending on the number of extra X
chromosomes and how many cells in the body are affected.
Symptoms may include a lack of fully developed secondary male
sexual characteristics—such as the growth of the testicles and
penis, deeper voice, and body hair—by adulthood. These men
usually cannot father children (are infertile). Other symptoms
may include delayed speech development, poor verbal skills,
below-average intelligence, or emotional and behavioral
problems. Males with more than one extra X chromosome generally
have more severe symptoms. Klinefelter syndrome usually goes
undiagnosed until the preteen years (around ages 11 to 12), when
males often begin puberty. In some males, Klinefelter syndrome
is never diagnosed and does not cause pr