What Is Klinefelter Syndrome?
Klinefelter syndrome is a chromosomal condition that affects male sexual development. Most males with Klinefelter syndrome have an extra X chromosome in each cell. Because their testicles do not develop normally, affected males may have low levels of the hormone testosterone when they reach puberty.
How Common Is Klinefelter Syndrome?
Klinefelter syndrome affects 1 in 500 to 1,000 males. Variants of Klinefelter syndrome are much rarer, occurring in 1 in 50,000 or fewer male births. Females are not affected by Klinefelter syndrome.
The Cause of Klinefelter Syndrome
The cause of Klinefelter syndrome is the presence of one (or more) extra X chromosome in a male's cells. Extra copies of genes on the X chromosome interfere with male sexual development, preventing the testicles from functioning normally and reducing the levels of testosterone in the body.
While Klinefelter syndrome is genetic (in that it involves an extra X chromosome gene), it is not usually hereditary in the conventional sense. That is, Klinefelter syndrome is not inherited, nor does it "run in families." Klinefelter syndrome is usually the result of a random event that occurs during the formation of reproductive cells (eggs and sperm).
Symptoms of Klinefelter Syndrome
While many men have an extra X chromosome, not a lot actually have symptoms of Klinefelter syndrome. Many men live out their lives without ever suspecting that they have an additional chromosome.
When an extra chromosome does cause
Klinefelter syndrome symptoms, the symptoms can vary among individual males. Some men may have many Klinefelter syndrome symptoms; others only a few.
Klinefelter syndrome symptoms can include:
- Breast development (gynecomastia). Ten percent of males with Klinefelter syndrome will develop breasts large enough to embarrass them.
- Reduced facial and body hair.
- Infertility (see Klinefelter Syndrome and Infertility).
- Small testes.
- Obesity.
- Being taller than their father or brothers.
- Learning disabilities.
- Problems with speech and language development.
Diagnosing Klinefelter Syndrome
Because they often don't appear any different from anyone else, many males with the XXY chromosome arrangement probably never learn of their extra chromosome. However, if a Klinefelter diagnosis is to be made, chances are greatest that it will be made at one of the following times in life:
- Before or shortly after birth
- Early childhood
- Adolescence
- Adulthood.
For males in which Klinefelter syndrome is suspected, a special blood test is recommended to confirm the diagnosis.
Treating Klinefelter Syndrome
Treatments for Klinefelter syndrome may include:
Counseling for parents of males with Klinefelter syndrome -- as well as for the males themselves -- at different stages of development has been shown to be beneficial.
Klinefelter Syndrome and Other Medical Problems
Because of these medical conditions and their complications (such as
heart disease), a person with Klinefelter syndrome is at increased risk of premature death.
Klinefelter Syndrome: The Prognosis
The
prognosis of Klinefelter syndrome is good, provided the patients have careful and consistent monitoring of their health and early identification and treatment of any problems that occur. Many men with Klinefelter syndrome lead full and active lives, and can expect a normal lifespan.
History of Klinefelter Syndrome
In 1942, Dr. Harry Klinefelter and his coworkers at the Massachusetts General Hospital in Boston published a report about 9 men who had enlarged breasts, sparse facial and body hair, small testes, and an inability to produce sperm.
By the late 1950s, researchers discovered that men with Klinefelter syndrome, as this group of symptoms came to be called, had a different chromosomal arrangement, XXY, instead of the usual male arrangement, XY.
Other Names for Klinefelter Syndrome
Other names for Klinefelter syndrome include:
- Klinefelter's syndrome
- 47,XXY
- XXY syndrome
- XXY trisomy.
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