What is Klinefelter syndrome?

Quick Answer
A male chromosomal disorder causing infertility and significantly feminized appearance
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Causes and Symptoms

Klinefelter syndrome is caused by a variation in the number of sex chromosomes. Males normally possess one X and one Y chromosome, while females normally have two X chromosomes. When an embryo has two X chromosomes and one Y chromosome (XXY), normal development and reproductive function are hampered, and the boy shows the symptoms of Klinefelter syndrome. These symptoms include breast development, underdevelopment of sex organs, and school or social difficulties. The major symptom is sterility or very reduced fertility, although affected males have normal erections. The testes remain small after puberty and produce few, if any, sperm. Sex drive may also be low.

In adolescence, breast tissue often develops significantly. In addition, normal facial and body hair may not develop in these boys. Although they usually grow quite tall, young men with Klinefelter syndrome often have disproportionate limbs and are less physically strong or coordinated than their peers. Some affected individuals exhibit some degree of subnormal intelligence. Others lack self-confidence or experience difficulties in learning language and speech or in concentrating.

Treatment and Therapy

Klinefelter syndrome is diagnosed using a karyotype, an analysis of the chromosomes from blood or cheek cells. It can determine the presence of forty-seven chromosomes, including one Y and two X. Although Klinefelter syndrome is genetic and cannot be cured, testosterone can be administered orally, intravenously, or transdermally to supplement the usually insufficient amount produced by the boy’s own testes. This therapy should enhance male physical development by increasing the size of the penis, causing hair growth and greater muscle bulk, and deepening the voice. Other benefits may include increased concentration, greater physical strength and energy, and higher sex drive.

Hormone therapy cannot increase the size of the testes, cure sterility, or reverse breast tissue development, which can only be treated by surgical removal. It may, however, increase self-esteem and a sense of masculinity, thereby easing social interactions.

For children with Klinefelter syndrome who experience difficulty with language development, early speech therapy interventions and educational assistance are recommended. Counseling and behavioral training may help with social interaction.

Perspective and Prospects

Found in about one out of every five hundred born, Klinefelter syndrome is the most common human chromosomal variation. Described by Harry Klinefelter in 1942, its cause was discovered by Patricia Jacobs and John Strong in 1959.

Men with Klinefelter syndrome are at higher risk of developing heart or lung disease, diabetes, hypothyroidism, dental complications, osteoporosis, breast or lung cancer, venous disease, depression, and autoimmune disorders. Nevertheless, the average life expectancy for those with Klinefelter syndrome is about the same as men without the condition.


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