Klinefelter Syndrome

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What is Klinefelter syndrome?

Klinefelter syndrome is a genetic disorder 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 some physical traits unusual for males.

Many men with an extra X chromosome are not aware that they have it, and they lead normal lives. Males with Klinefelter syndrome may be described as XXY males or males with XXY syndrome. 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 cells split unevenly to produce eggs. But it can also occur when cells split unevenly to produce sperm.

What are the symptoms?

Many men with 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 cannot father children, 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 normally 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.

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 a boy have more normal body development.

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

Frequently Asked Questions

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	Growth and development: Helping your child build self-esteem

There generally are no obvious signs of Klinefelter syndrome until puberty. At this time, boys with Klinefelter syndrome often do not have the increase in testosterone levels that normally occurs.

Because of low testosterone levels, boys with Klinefelter syndrome may:

• Have sparse pubic, facial, and body hair.
• Have underdeveloped muscles.
• Have enlarged breasts (gynecomastia).
• Be taller than other males in their family and have long legs, narrow shoulders, and wide hips.

Most men with Klinefelter syndrome have smaller-than-expected testicles. And many men are infertile and cannot father children without using special fertility techniques.

See a picture of a male with Klinefelter syndrome.

Mental, emotional, and behavioral concerns

Males with Klinefelter syndrome appear to have reduced abilities in specific areas, including:¹

• Language development. Boys with Klinefelter syndrome often have delayed or slowly developing speech skills and poor verbal skills.
• Critical thinking skills, problem solving, and ability to plan.
• Multi-tasking.
• Impulse control.
• Response time.

Some research shows that these problems with learning and behavior may be caused by the way the brain grows in males who have Klinefelter syndrome.²

Boys may have emotional problems that range from being shy and immature to being overly anxious or aggressive. They may also have poor social skills, which may cause problems for them in school and in other social situations. They are at risk for developing psychiatric disorders, such as anxiety, depression, and drug and alcohol abuse.

Klinefelter syndrome can be detected before birth (prenatally) through amniocentesis or chorionic villus sampling (CVS). But this is not routinely done. It is usually diagnosed in childhood, during puberty, or in adulthood by a medical history, physical exam, and a chromosome test called a karyotype. Other lab tests, such as hormone tests or a semen analysis, may be done if Klinefelter syndrome is suspected.

Testing in childhood or during puberty

Klinefelter syndrome usually is not diagnosed before the preteen years because there are no symptoms or because symptoms go unnoticed until puberty. But a doctor may suspect Klinefelter syndrome when a young boy has difficulty learning to talk, read, or write.

During puberty, some males may be suspected of having Klinefelter syndrome, including those who:

• Are taller than other males in their family and have long legs.
• Have small testicles that do not increase in size as puberty progresses.
• Have enlarged breast tissue that persists for more than 2 years.
• Have learning or social problems (such as lacking self-confidence and being shy, immature, or dependent).
• Have mild mental retardation. Klinefelter syndrome is present in about 1 out of 100 males who have mental retardation.³

Tests for Klinefelter syndrome during childhood or puberty usually include a medical history, physical exam, and karyotype.

Adult testing

Klinefelter syndrome may not be diagnosed until adulthood when a man seeks medical care to find out the cause of his infertility. About 3 out of 100 infertile men have Klinefelter syndrome.⁴ Tests include a medical history, physical exam, and karyotype. A man may also have hormone tests and a semen analysis.

Replacement of the hormone testosterone is the main treatment for Klinefelter syndrome. Other treatments vary depending on the symptoms and may include help for language and learning difficulties and counseling or social skills training for behavior problems.

Initial treatment

Treatment for Klinefelter syndrome usually starts in adolescence. It starts with measuring the amount of testosterone and other hormones in his blood. Many teenage boys with Klinefelter syndrome don't have low levels of testosterone.⁵ If a boy's testosterone level is low, he is given a man-made form of testosterone (Depo-Testosterone) on a regular basis. Testosterone can be given as an injection or through a skin patch or gel.

Testosterone:

• Increases body hair, mainly on the face (beard), under the arm (axillary), and in the genital area (pubic).
• Increases muscle development.
• Increases sex drive.
• Helps prevent osteoporosis.
• May prevent or shrink enlarged breasts.
• Provides better self-esteem by allowing the boy to "fit in" with his peers. This can result in more successful interpersonal relationships.

Side effects of testosterone replacement therapy are uncommon but include acne getting worse, overly rapid sexual development, and behavior problems (such as being overly aggressive). Careful monitoring is important to prevent these side effects.

Ongoing treatment

Ongoing treatment for Klinefelter syndrome may include:

• Help for language and learning difficulties. If language delays are identified in early childhood, educational assistance and speech therapy can be used to treat the problem. Children with learning difficulties can receive help through the school system.
• Testosterone replacement. This is given by injection or through a skin patch or gel. Testosterone replacement usually continues throughout the man's life but does not help infertility. For men who want to start a family, counseling and treatment at a fertility clinic are generally recommended.
• Regular medical checkups to watch for other conditions, such as autoimmune diseases, behavior problems, or psychiatric disorders, such as depression. Counseling or medicine may be needed.

Home treatment for Klinefelter syndrome is directed at understanding your son's emotional, physical, behavioral, and learning needs. 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 a genetic disorder and was 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 the disorder. 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.
• 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.

Growth and development: Helping your child build self-esteem

If you suspect Klinefelter syndrome

Sexual development (such as growth of the penis, testicles, and facial hair) and muscle development are very important to teenage boys. A boy who is not developing like other boys his age may be afraid of being rejected and ridiculed by his peers. Early diagnosis and treatment for Klinefelter syndrome may prevent some of this. Talk to your doctor if your preteen or teenager is not developing like other boys his age, is behind in school or having behavior problems, or has unusually long legs compared with other family members. See a picture of a male with Klinefelter syndrome.

Organizations

Related Information

• Genetics
• Growth and Development, Ages 11 to 14 Years
• Growth and Development, Ages 15 to 18 Years
• Growth and Development, Ages 6 to 10 Years
• Gynecomastia

Citations

1. Lanfranco F, et al. (2004). Klinefelter's syndrome. Lancet, 364(9430): 273–283.

2. Gledd JN, et al. (2007). XXY (Klinefelter syndrome): A pediatric quantitative brain magnetic resonance imaging case control study. Pediatrics, 119(1): 232–240.

3. Elias ER, et al. (2009). Klinefelter syndrome (XXY) section of Genetics and dysmorphology. In WW Hay et al., eds., Current Diagnosis and Treatment: Pediatrics, 19th ed., p. 1002. New York: McGraw-Hill.

4. Rapaport R (2007). Klinefelter syndrome section of Development and function of the gonads. In RM Kliegman et al., eds., Nelson Textbook of Pediatrics, 18th ed., p. 2380–2382. Philadelphia: Saunders Elsevier.

5. Wikstrom AM, et al. (2006). Are adolescent boys with Klinefelter syndrome androgen deficient? A longitudinal study of Finnish 47,XXY boys. Pediatric Research, 59(6): 854–859.

Other Works Consulted

• 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 (2007). Klinefelter's syndrome (XXY seminiferous tubule dysgenesis) section of Testes. In DG Gardner, D Shoback, eds., Greenspan's Basic and Clinical Endocrinology, 8th ed., pp. 482–484. New York: McGraw-Hill.

• Styne DM, Grumbach MM (2008). Klinefelter's syndrome and its variants section of Puberty: Ontogeny, neuroendocrinology, physiology, and disorders. In HM Kronenberg et al, eds., Williams Textbook of Endocrinology, 11th ed., pp. 1051–1053. Philadelphia: Saunders Elsevier.