Klinefelter Syndrome

(47 XXY Syndrome; KS)


Klinefelter syndrome (KS) happens in men who have more than one X chromosome (XXY).

Klinefelter Syndrome

Nucleus factsheet image
Copyright © Nucleus Medical Media, Inc.


Males have a single X chromosome from their mother and a single Y one from their father. Males with KS get at least one extra X from either parent.

Risk Factors

There are no known risk factors for KS.


Symptoms may not be found until puberty or later.

Children may have problems with:

  • Speech
  • Learning
  • Behavior

Teens may have:

  • Delayed puberty
  • Enlarged breasts

Adults may have:

  • Small, firm testes
  • Small penis
  • A poor sex drive or sexual problems
  • Lack of facial and body hair
  • Breast pain
  • Hot flashes, sweating


You will be asked about your symptoms and health history. A physical exam will be done.

KS is diagnosed with a genetic test. Blood tests may also be done.


KS is treated with:


Boys with KS have their hormone levels checked every year. If testosterone levels are low, then testosterone therapy may help. It may also help adults.

Speech and Language Therapy

This therapy should start early to avoid social and school problems. It may involve:

  • Speech therapy
  • Special services at school
  • Extra support and help with learning from parents and teachers
  • Social skills training and mental health counseling


KS can’t be prevented. If you are having fertility treatment, ask about genetic testing.


The Association for X and Y Chromosome Variations
National Institute of Child Health and Human Development


Canadian Psychiatric Association
Canadian Psychological Association


Klinefelter syndrome. EBSCO DynaMed Plus website. Available at: http://www.dynamed... . Updated March 6, 2017. Accessed July 6, 2018.
About 47, XXY (Klinefelter syndrome). Klinefelter Syndrome and Associates website. Available at: The Association for X and Y Chromosome Variations. Accessed July 6, 2018.
Klinefelter syndrome (KS): Overview. National Institute of Child Health and Human Development website. Available at:
...(Click grey area to select URL)
Accessed July 6, 2018.
Last reviewed May 2018 by Kari Kassir, MD
Last Updated: 7/6/2018

EBSCO Information Services is fully accredited by URAC. URAC is an independent, nonprofit health care accrediting organization dedicated to promoting health care quality through accreditation, certification and commendation.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

To send comments or feedback to our Editorial Team regarding the content please email us at healthlibrarysupport@ebsco.com. Our Health Library Support team will respond to your email request within 2 business days.