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Klinefelter Syndrome



  • Klinefelter syndrome (KS) is a genetic disorder that affects only men and boys. Most males with KS can lead healthy, normal lives.
  • Many boys with KS do not need treatment. Testosterone treatment may be helpful for some boys.


What is Klinefelter syndrome?

Klinefelter syndrome (KS) is a genetic disorder that affects only men and boys. Most males with KS can lead healthy, normal lives. However, most men with KS are unable to father a child the natural way.

What is the cause?

Human bodies are made up of cells. Inside the cells are tiny structures called chromosomes. Usually, a female has 2 X chromosomes (XX) and a male has 1 X and 1 Y (XY). But in Klinefelter syndrome, a boy is born with an extra copy of the X chromosome (XXY). What causes this extra chromosome and how it causes the problems of Klinefelter’s syndrome is not known.

The risk of having a child with KS increases as a woman gets older, and the risk is greatest when the mother is over 35 years of age.

What are the symptoms?

Klinefelter syndrome doesn't usually cause symptoms in childhood, and many boys and men don’t know that they have it. Possible symptoms may include:

  • Loose or floppy muscles
  • Small penis and testicles
  • Teens may have enlarged breasts, long arms and legs, and be taller than others in the family

Boys may:

  • Be slower than most children in learning to walk, feed themselves, and talk
  • Be shy and have trouble expressing feelings, possibly because of slower language development
  • Have trouble reading and writing
  • Be clumsy or lack coordination

Most boys with KS do not have behavior problems. However, they may have trouble paying attention. Boys with KS are also at higher risk for diabetes, but the reason for this is not known.

How is it diagnosed?

Klinefelter syndrome may be diagnosed before birth based on:

  • Chorionic villus sampling, or CVS, which tests a sample of cells from the placenta
  • Amniocentesis, which uses a needle put into the mother's belly to get samples of the fluid that surrounds the baby in the uterus

The diagnosis may also be made later in life by a blood test that checks your child’s chromosomes.

What is the treatment?

Many boys with KS do not need treatment. Most will need testosterone treatment in adulthood. Testosterone treatment may be helpful to boys with KS who are overweight. Speech, language, or physical therapy may be helpful if your child has problems with talking, walking, or learning.

How can I help take care of my child?

  • Build your child's self-esteem. A boy may have trouble in school and may not feel good about himself simply because he looks different. He may withdraw from friends and social activities. You can build up your child's self-esteem if you remind him of his strengths. Do this regularly. Your child may need counseling to help change views and expectations about himself.
  • Learn about your child’s condition. Knowing how KS affects your child helps you better understand how treatments, medicines, and lifestyle changes can help. Know when you should call your child’s healthcare provider about your child’s symptoms.
  • Take care of your child’s health. Make sure your child eats a variety of healthy foods and gets enough sleep and physical activity every day. Teach children and teens to avoid alcohol, caffeine, nicotine, and drugs.

For more information, contact:

Developed by Change Healthcare.
Pediatric Advisor 2022.1 published by Change Healthcare.
Last modified: 2022-01-03
Last reviewed: 2018-11-09
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2022 Change Healthcare LLC and/or one of its subsidiaries
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