Health Encyclopedia

Klinefelter syndrome

Definition

Klinefelter syndrome is the presence of an extra X chromosome in a male.

Alternative Names

47 X-X-Y syndrome

Causes, incidence, and risk factors

Humans have 46 chromosomes. Chromosomes contain all of your genes and DNA, the building blocks of the body. The two sex chromosomes determine if you become a boy or a girl. Females normally have two of the same sex chromosomes, written as XX. Males normally have an X and a Y chromosome (written as XY).

Klinefelter syndrome is one of a group of sex chromosome problems. It results in males who have at least one extra X chromosome. Usually, this occurs due to one extra X (written as XXY).

Klinefelter syndrome is found in about 1 out of every 500 - 1,000 newborn males. Women who have pregnancies after age 35 are slightly more likely to have a boy with this syndrome than younger women.

Symptoms

The most common symptom is infertility. Other symptoms may include:

Abnormal body proportions (long legs, short trunk, shoulder equal to hip size)
Enlarged breasts (gynecomastia)
Sexual problems
Less than normal amount of pubic, armpit, and facial hair
Small, firm testicles
Small penis
Tall height

Signs and tests

Adults may come to the doctor because of infertility. School-age children may be brought in to because of learning problems.

The following tests may be performed:

Karyotyping
Semen count
Serum estradiol levels (a type of estrogen)
Serum follicle stimulating hormone
Serum luteinizing hormone
Serum testosterone

Treatment

Testosterone therapy may be prescribed. This can help:

Grow body hair
Improve appearance of muscles
Improve concentration
Improve mood and self esteem
Increase energy and sex drive
Increase strength

Most men with this syndrome are not able to father children. However, some men have been able to have children. An infertility specialist may be able to help.

Support Groups

The American Association for Klinefelter Syndrome Information and Support (AAKSIS) - www.aaksis.org

Expectations (prognosis)

Most patients have a normal, productive life.

Complications

The syndrome increases the risk of:

Attention deficient hyperactivity disorder
Autoimmune disorders such as lupus, rheumatoid arthritis, and Sjogren syndrome
Breast cancer
Depression
Dyslexia
Extragonadal germ cell tumor (a rare tumor)
Learning disabilities, despite normal or high IQ
Lung disease
Osteoporosis
Varicose veins

Enlarged teeth with a thinning surface (taurodontism) is very common in Klinefelter syndrome. It can be diagnosed by dental x-rays.

Calling your health care provider

Call for an appointment with your health care provider if a boy does not develop secondary sexual characteristics at puberty.

A genetics counselor can provide information about this condition, and help explain abnormal chromosome findings and possible complications. The counselor will also be familiar with local and national support groups.

An endocrinologist and infertility specialist may also be helpful.

Review Date:10/15/2008
Reviewed By:Diana Chambers, MS, EdD, Certified Genetics Counselor (ABMG), Charter Member of the ABGC, University of Tennessee, Memphis, TN. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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