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Klinefelter's Syndrome

Klinefelter's syndrome, or XXY syndrome, is a genetic disorder that afflicts 1 in 500 to 1,000 males. Males usually have one X and one Y chromosome (women have two X chromosomes); however, Klinefelter men are born with at least one extra X chromosome (in rare cases they are born with three or four X-chromosomes). Because of this extra X chromosome, affected males are usually referred to as "XXY males" or "47,XXY males." Klinefelter's syndrome is one of the most common genetic abnormalities, according to the National Institutes of Health, and the vast majority of men born with this condition are infertile, accounting for approximately 3 percent of all infertile men.

Although Klinefelter's syndrome is found more often in children born to older mothers and, to a certain extent, older fathers, a definitive cause of the condition has not been identified. Babies born with Klinefelter's appear normal at birth and many young boys develop normally, although they may learn to speak later than other children and have difficulty reading and writing, and most have some language impairment. However, XXY males produce approximately half the testosterone of normal boys during puberty, resulting in decreased facial and pubic hair and immature and undeveloped sperm. The testicles of XXY males also tend to be smaller and firmer than usual.

XXY males may have varying degrees of physical characteristics, such as greater than normal height, breast development (gynecomastia), a rounded body type, and a youthful build and facial appearance. However, these characteristics may be very slight and go unnoticed. The only way to confirm Klinefelter's syndrome is through karyotyping, or photographing the chromosomes for analysis by a professional. According to the American Academy of Family Physicians, Klinefelter's isn't discovered until adulthood in 25 percent of cases, often when men undergo infertility testing.

A typical ejaculation from a male with a normal chromosomal makeup contains approximately 200 million sperm; however, an ejaculation from an XXY male contains only a few thousand sperm or no sperm at all. Occasionally, mosaic Klinefelter's syndrome can occur when some of the cells in the man's body have an extra X chromosome and the other nave a normal XY chromosome arrangement. These men may have the same or milder symptoms than those with non-mosaic Klinefelter's, and retain normal testicular function and fertility.

Testosterone supplements can help restore secondary male characteristics, such as beard growth, muscle mass, and increased libido; however, there is no treatment for XXY infertility and ART procedures are necessary for conception. If tests reveal the presence of some sperm in the XXY male's testes, testicular sperm extraction and intracytoplasmic sperm injection (ICSI) may be performed. If this is impossible or unsuccessful, sperm donation and adoption are viable options.

Klinefelter's may be passed on to children, so embryos of affected individuals should be tested for chromosomal abnormalities. This can be done with chorionic villus sampling or amniocentesis; however both of these procedures carry a slight risk of miscarriage.



Featured Sites:

Cord Blood Registry
March of Dimes
Susan G. Komen

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