Klinefelter Syndrome

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Klinefelter Syndrome

Klinefelter Syndrome

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

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

See a picture of a
male with Klinefelter syndrome.

How is Klinefelter syndrome diagnosed?

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

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

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

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
  • 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.

Frequently Asked Questions

Learning about Klinefelter syndrome:

Ongoing concerns:

  • What complications can develop?

Other Places To Get Help


Eunice Kennedy Shriver National Institute of Child Health and Human Development (U.S.)

Endocrine Society: Hormone Health Network (U.S.)


Other Works Consulted

  • Achermann JC, Hughes IA (2011). Disorders of Sex Development. In S Melmed et al., eds., Williams Textbook of Endocrinology, 12th ed., pp. 868–934. Philadelphia: Saunders.
  • Bojesen A, et al. (2003). Prenatal and postnatal prevalence of Klinefelter syndrome: A national registry study. Journal of Clinical Endocrinology and Metabolism, 88(2): 622–626.
  • Braunstein GD (2011). Testes. In DG Gardner, D Shoback, eds., Greenspan's Basic and Clinical Endocrinology, 9th ed., pp. 395–422. New York: McGraw-Hill Medical.
  • Saenz M et al. (2014). Genetics and dysmorphology. In WW Hay Jr, et al., eds., Current Diagnosis and Treatment: Pediatrics, 22nd ed., pp. 1134–1170. New York: McGraw-Hill.


ByHealthwise StaffPrimary Medical Reviewer John Pope, MD - Pediatrics Martin J. Gabica, MD - Family Medicine Adam Husney, MD - Family Medicine Kathleen Romito, MD - Family Medicine Specialist Medical Reviewer Siobhan M. Dolan, MD, MPH - Reproductive Genetics

Current as ofFebruary 23, 2018