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Genetic and Rare Diseases Information Center (GARD)

Klinefelter syndrome

Other Names for this Disease
  • Klinefelter's syndrome
  • XXY syndrome
Related Diseases
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Your Question

My husband has Klinefelter syndrome. I have read a lot of things about this syndrome, but I want to know more about the future. He is 33-years-old, and he didn't take any medication for Klinefelter syndrome in the past. What is the chance of him becoming a father?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is Klinefelter syndrome?

Klinefelter syndrome (KS) is a condition that may be present in an individual that has two X chromosomes and one Y chromosome (47, XXY); usually, males have one X and one Y (XY) and females have two X chromosomes (XX). Some individuals with a 47, XXY chromosome finding may have no obvious signs or symptoms of KS while others may have several features and varying degrees of cognitive, social, behavioral, and learning difficulties.[1] Because features may not be apparent until mid to late adolescence, the term “Klinefelter syndrome” is often reserved for affected adolescents and adults. Although the vast majority of boys with KS identify as males, some individuals develop atypical gender identities.[2] In adulthood, individuals with Klinefelter syndrome may have primary hypogonadism (decreased testosterone production), small testes, enlarged breast tissue (gynecomastia), tall stature, and/or other features.[1] The vast majority of males with KS are infertile, but many produce sperm and may be able to conceive with assisted reproduction. Treatment varies among individuals and may include testosterone therapy; however, this therapy may not be appropriate for all individuals.[2]
Last updated: 9/20/2013

What are the signs and symptoms of Klinefelter syndrome?

Because XXY males do not really appear different from other males and because they may not have any or mild symptoms, XXY males often don't know they have Klinefelter syndrome (KS).   Whether or not a male with KS has visible symptoms depends on many factors, including how much testosterone his body makes, if he is mosaic (with both XY and XXY cells), and his age when the condition is diagnosed and treated.[3]   Symptoms may include:

  • Abnormal body proportions (long legs, short trunk, narrower shoulders and wider hips)
  • Breast growth (gynecomastia)
  • Infertility: Nearly all men with KS are unable to father a biologically-related child without help from a fertility specialist.
  • Decreased sexual interest
  • Less than normal amount of pubic, armpit, and facial hair
  • Small, firm testicles
  • Tall height

Boys with Klinefelter syndrome may also have learning disabilities and difficulty with speech and language development. They tend to be quiet, sensitive, and unassertive, but personality characteristics vary among males with this condition. [4]

Last updated: 3/3/2010

Is Klinefelter syndrome inherited?

This condition is not inherited, but usually occurs as a random event during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may gain one or more extra copies of the X chromosome as a result of nondisjunction. If one of these reproductive cells contributes to the genetic makeup of a child, the child will have one or several extra X chromosomes in each of the body's cells.[5]
Last updated: 3/19/2013

How might Klinefelter syndrome be treated?

Because symptoms of Klinefelter syndrome (KS) can sometimes be very mild, many individuals are never diagnosed or treated. The type of therapies available for individuals seeking treatment depends on the type of symptoms present. There are conflicting opinions in some of the literature about when treatment should be started and who should be treated. The earlier in life that KS symptoms are recognized and treated (for example, by early puberty), the more likely it is that the symptoms can be reduced or eliminated. However, although the majority of boys with KS grow up to live as males, some reportedly develop atypical gender identities. For these individuals, certain therapies (such as supplemental testosterone) may not be suitable. Gender identity should be discussed with health care providers before starting treatment.[6]

Management options available to individuals with signs and symptoms of Klinefelter syndrome may include:
  • Educational interventions – As children, many individuals with Klinefelter syndrome qualify for special services to help them in school. Teachers can also help by using certain methods in the classroom, such as breaking bigger tasks into small steps.
  • Therapeutic options – A variety of therapists, such as physical, speech, occupational, behavioral, mental health, and family therapists, can often help reduce or eliminate some of the symptoms of Klinefelter syndrome such as poor muscle tone, speech and language problems, or low self-confidence.
  • Medical management – About half of individuals with KS have low testosterone levels, which may be raised by taking supplemental testosterone. Having a more normal testosterone level can help individuals develop bigger muscles, a deeper voice, and facial and body hair. Many healthcare providers recommend testosterone therapy when a boy reaches puberty. However, not all males with KS benefit from testosterone therapy, and this therapy also may not be suitable for some individuals depending on gender identity.[7][6] Some individuals may opt to have breast removal or reduction surgery.[6]
Last updated: 9/20/2013

Are individuals with Klinefelter syndrome able to have children?

Although the vast majority of individuals with Klinefelter syndrome (KS) are azoospermic (have no sperm present in the ejaculate), motile sperms in the ejaculate and even spontaneous pregnancies resulting from fathers with KS have been described, although such cases are rare. In general, individuals with mosaic KS (those that also have a 46,XY cell line) are less severely affected and the chance of finding sperm in the ejaculate in these individuals is significantly higher than in non-mosaic cases. In the past, the use of donor semen (or more rarely by adoption) had been the only possible way of having a child. However, in recent years, testicular sperm extraction (TESE) followed by intracytoplasmic sperm injection (ICSI) have resulted in more than 100 cases of individuals with KS worldwide who became biological parents.[8]

Individuals with KS who would like to have children should discuss their options with their personal healthcare provider. Individuals with Klinefelter syndrome should not automatically assume they are infertile without thorough testing.[7]
Last updated: 9/18/2013

Other Names for this Disease
  • Klinefelter's syndrome
  • XXY syndrome
Related Diseases
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.