Your browser does not support javascript:   Search for gard hereSearch for news-and-events here.

Diseases

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

Klinefelter syndrome can be caused by nondisjunction. What increases the risk of males or females to have nondisjunction during meiosis? What research is currently underway for Klinefelter syndrome?

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 occurs in males when they have an extra X chromosome. Some males with KS have no obvious signs or symptoms while others may have varying degrees of cognitive, social, behavioral, and learning difficulties. Adults with Klinefelter syndrome may also experience primary hypogonadism (decreased testosterone production), small testes, enlarged breast tissue (gynecomastia), tall stature, and/or infertility. KS is not inherited, but usually occurs as a random event during the formation of reproductive cells (eggs and sperm). Treatment is based on the signs and symptoms present in each person.[1][2][3]
Last updated: 10/13/2015

What is nondisjunction and how does it result in Klinefelter syndrome?

Nondisjunction is an error in cell division. The cells destined to become sperm and eggs undergo a process known as meiosis. In this process, the 46 chromosomes in the cell separate, ultimately producing two new cells having 23 chromosomes each. Before meiosis is completed, however, chromosomes pair with their corresponding chromosomes and exchange bits of genetic material. In women, X chromosomes pair; in men, the X and Y chromosome pair. After the exchange, the chromosomes separate, and meiosis continues.[1]

In some cases, the two X chromosomes or the X chromosome and Y chromosome fail to pair and fail to exchange genetic material. Occasionally, this results in their moving independently to the same cell, producing either an egg with two Xs, or a sperm having both an X and a Y chromosome. When a sperm having both an X and a Y chromosome fertilizes an egg having a single X chromosome, or a normal Y- bearing sperm fertilizes an egg having two X chromosomes, an XXY male is conceived.[1]
Last updated: 10/13/2015

What causes nondisjunction?

The cause of nondisjunction is unknown. Nondisjunction seems to be a chance event. Nothing that a person does or doesn't do during their reproductive years can cause these chromosomal changes. We do know that nondisjunction occurs more frequently in the eggs of women as they get older.[4]
Last updated: 10/13/2015

How can I learn about research involving Klinefelter syndrome?

The U.S. National Institutes of Health, through the National Library of Medicine, developed ClinicalTrials.gov to provide patients, family members, and members of the public with current information on clinical research studies. You can find clinical trials for individuals with Klinefelter syndrome by clicking on the above link. Check this site often for regular updates.

You can also contact the Patient Recruitment and Public Liaison (PRPL) Office at the National Institutes of Health (NIH). We recommend calling the toll-free number listed below to speak with a specialist, who can help you determine if you are eligible for any clinical trials.   If you are located outside the United States, and would like to be contacted via telephone, you will need to provide your telephone number in full, including area code and international dialing prefix.

Patient Recruitment and Public Liaison Office
NIH Clinical Center
Bethesda, Maryland 20892-2655
Toll-free: 800-411-1222
Fax: 301-480-9793
Email:  prpl@mail.cc.nih.gov
Web site:  http://clinicalcenter.nih.gov/

You can find helpful general information on clinical trials at the following ClinicalTrials.gov Web page.
http://clinicaltrials.gov/ct2/info/understand

A tutorial about clinical trials that can also help answer your questions can be found at the following link from the National Library of Medicine:
http://www.nlm.nih.gov/medlineplus/tutorials/cancerclinicaltrials/htm/lesson.htm

Last updated: 10/13/2015

References
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.