What Is Klinefelter's Syndrome?

A Genetic Condition Affecting Males

An illustration of chromosomes.
An illustration of chromosomes. Science Photo Library - SCIEPRO/Getty Images

Klinefelter's syndrome is a genetic condition that affects only males. Here's what you should know about the causes, symptoms and treatment options for the condition.

What Is Klinefelter's Syndrome?

Klinefelter's syndrome is a genetic abnormality that affects only males. Named after the American physician Harry Klinefelter in 1942, Klinefelter's syndrome affects approximately one in 1,000 males, making it a very common genetic abnormality.

The disease is characterized by an abnormality in chromosomes or genetic material. A person's sex is determined by X and Y chromosomes. Males usually have one X and one Y chromosome (an XY arrangement), but those Klinefelter's syndrome have an extra X chromosome (an XXY arrangement). This extra copy of the X chromosome can interfere with sexual development and fertility.

Although the extra sex chromosome is common, the syndrome and its signs and symptoms are not: Most men with an extra X chromosome never realize they have an additional chromosome.

Causes of Klinefelter's Syndrome

Klinefelter's syndrome is caused by a random genetic error that occurs during the formation of the egg or sperm, or after conception, and is not an inherited disease. Women who give birth after the age of 35 have a slightly higher incidence of Klinefelter's syndrome, so some experts believe that this could be one cause.

Symptoms of Klinefelter's Syndrome

As mentioned, many men can live with an extra X chromosome and experience no symptoms. However, in those who develop Klinefelter's syndrome, these symptoms are common:

  • Abnormal body proportions (usually the tendency to have long legs and a short trunk)

Some males are diagnosed during their adolescence when their testes do not develop as they should. However, many men do not realize they have Klinefelter's until they are trying to start a family of their own, as men with the condition do not produce sperm and are therefore infertile. Genetic tests will show the presence of an extra X chromosome and are the most effective way to diagnose Klinefelter's.

Treatment Options for Klinefelter's Syndrome

Testosterone therapy is the most common form of treatment for Klinefelter's syndrome and can have a number of positive effects, including improving sex driving, promoting hair grown and increasing muscle strength. Most men with Klinefelter's are never able to father a child but are able to live fulfilled lives with treatment.

For more information about Kleinfelter's syndrome, read these other helpful articles:

A Guide for XXY Males and Their Families

Klinefelter's Syndrome and Breast Cancer

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