Topic Overview

What is Klinefelter syndrome?

Klinefelter syndrome is a genetic condition that affects males. Klinefelter syndrome occurs when a boy is born with one or more extra X chromosomes. Most males have one Y and one X chromosome. Having extra X chromosomes can cause a male to have a variety of physical traits.

Many men with an extra X chromosome are not aware that they have it, and they lead normal lives. Klinefelter syndrome occurs in about 1 out of 1,000 males.

What causes Klinefelter syndrome?

The presence of an extra X chromosome in males most often occurs when the genetic material in the egg splits unevenly. But it can also occur when the genetic material in the sperm splits unevenly. Even though Klinefelter syndrome is a genetic disorder, it is not passed down through families. So, parents who have a child with Klinefelter syndrome are not any more likely than other couples to have another child with the condition.

What are the symptoms?

Many men who have Klinefelter syndrome do not have obvious symptoms. Others have sparse body hair, enlarged breasts, and wide hips. In almost all men the testicles remain small. In some men the penis does not reach adult size. Their voices may not be as deep. They usually have infertility. But they can have a normal sex life.

Some boys with Klinefelter syndrome have language and learning problems.

See a picture of a male with Klinefelter syndrome.

How is Klinefelter syndrome diagnosed?

Klinefelter syndrome usually is not diagnosed until the time of puberty. At this point, the boy’s testicles fail to grow and you may start to notice other symptoms.

To find out if your son has Klinefelter syndrome, your doctor will ask questions about his past health, do a physical exam, and order a chromosome test called a karyotype.

In adult men, lab tests in addition to a karyotype may be done, such as hormone tests or a semen analysis, if Klinefelter syndrome is suspected.

Sometimes Klinefelter syndrome is found before a baby is born (prenatally). Genetic tests on cells collected from amniocentesis or chorionic villus sampling (CVS) can show when a baby boy has Klinefelter syndrome. So the condition may be found when a pregnant woman has genetic tests for another reason.

How is it treated?

Males with Klinefelter syndrome can be given testosterone, a hormone needed for sexual development. If treatment is started around the age of puberty, it can help boys with the sexual development of their bodies.

Testosterone is given by injection or through a skin patch or gel. The treatment usually continues throughout a man’s life but does not help infertility.

Speech therapy and educational support can help boys who have language or learning problems.

How can you help your son?

If your son has been diagnosed with Klinefelter syndrome:

• Recognize your feelings. It is natural for parents to feel that they have done something to cause Klinefelter syndrome. But this condition is beyond anyone’s control. Allow yourself time to deal with your feelings, and talk with your son’s doctor about your concerns.
• Educate yourself about this condition. The common problem for parents is fear of the unknown. Educating yourself will help you learn how to help your son.
• Support your son. Provide education appropriate for his age about Klinefelter syndrome and give him the emotional support and encouragement he needs. Remind him that most men who have Klinefelter syndrome go through life with few problems.
• Be actively involved in your son’s care. Talk with your doctor about his treatment. If counseling for behavioral problems is needed, or if your son has difficulty reading or has poor verbal skills, get help from qualified professionals who have experience working with boys who have Klinefelter syndrome.
• Encourage your son to take part in activities to improve his physical motor skills, such as karate, soccer, basketball, baseball, or swimming. For more information, see the topic Physical Activity for Children and Teens.
• Work with your son’s teachers, principal, and school administrators.
  • Contact his teachers on a regular basis to compare how he is doing at home and at school.
  • When appropriate, let your son be present for talks with his teachers. Use brief notes, telephone calls, and meetings to identify and solve problems.
  • Provide articles and pamphlets to your son’s teachers and school principal about Klinefelter syndrome.
• Encourage your son’s independence. Although it is important to be supportive, realize that watching over your son too much can send the message that you think he is not able to do things on his own.