DiGeorge syndrome

Definition

Turner syndrome is a disorder of the chromosomes affecting females, where one of the two X chromosomes is partially or completely absent.

Description

Chromosomes are structures in the nucleus of every cell in the body. Chromosomes contain the genetic information necessary to direct the growth and functioning of all the cells and systems of the body. A normal person has a total of 46 chromosomes in each cell, two of which are responsible for determining the sex of that person. Normally, females have two X chromosomes and males have one X and one Y chromosome.

In Turner syndrome, an error very early in development results in an abnormal number and arrangement of chromosomes. Most commonly, a patient with Turner syndrome will be born with 45 chromosomes in each cell rather than 46. The missing chromosome is an X chromosome.

About 1 in every 8,000 babies born has Turner syndrome.

Causes & symptoms

No cause has been identified for Turner syndrome.

At birth, female babies with Turner syndrome are below average in weight and length. They have slightly swollen hands and feet, and sometimes have swelling at the nape of the neck. Girls with Turner syndrome are shorter than normal, and have short, webbed necks with extra, loose skin. The jaw is usually small and the ears are large. An extra fold of skin is often seen on either side of the nose, close to the eye (called an epicanthic fold). The chest is usually quite broad, with increased distance between the nipples.

Further examination of girls with Turner syndrome will reveal that the ovaries, normal at birth, begin to slowly disappear. Within about two years, the ovaries usually contain no eggs. By about 10 years of age, the ovaries themselves will be essentially gone, with only streaks of tissue remaining. Nearly all Turner syndrome patients have no eggs in their ovaries, and are unable to conceive. Various heart defects are more common in females with Turner syndrome, and about 33% of all patients will have kidney deformities.

Many patients have multiple middle ear infections, and hearing loss is a frequent problem. Coordination is often poor, and many babies with Turner syndrome learn to walk relatively late. Some language problems may exist, but testing usually reveals that patients have normal intelligence.

Some disorders occur more frequently in Turner syndrome patients. These include thyroid disorders, inflammatory bowel disease, and malformed blood vessels within the gastrointestinal tract.

Diagnosis

Diagnosis is made by studying the chromosomes. Patients with Turner syndrome will either lack all or a part of one X chromosome. The other X chromosome will be intact. It is important that careful analysis of the chromosomes be done in order to search for any pieces of Y chromosome present. Y chromosomes are usually present only in males. When Turner syndrome patients have pieces of a Y chromosome in their cells, they have a substantially increased risk of developing a type of tumor called a gonadoblastoma.

Once Turner syndrome has been diagnosed, it is important to perform careful ultrasound examination of the heart, kidneys, and ovaries to diagnose associated defects.

Treatment

There is no treatment available for Turner syndrome. However, girls are sometimes treated with growth hormones which can help them reach a more normal height. Because the ovaries are normally responsible for producing the female hormone estrogen, replacement estrogen therapy will be necessary.

Prognosis

The prognosis for a person with Turner syndrome is dependent on what (if any) other conditions are present. For example, heart or kidney defects, hearing loss, or the development of inflammatory bowel disease may significantly affect a person's quality of life. Without these types of conditions, however, a person with Turner syndrome can be expected to live a relatively normal life. Support will be necessary to help the adolescent girl cope with body image issues and to help some women accept the fact that they will never be able to have children.

Key Terms

Chromosomes

Spaghetti-like structures located within the nucleus (or central portion) of each cell. Chromosomes contain genes, structures that direct the growth and functioning of all the cells and systems in the body. Chromosomes are responsible for passing on hereditary traits from parents to child, and for determining whether the child will be male or female.

Ovaries

The female organs that contain the eggs for reproduction; ovaries also produce important hormones.

Further Reading

For Your Information

Books

• DiGeorge, Angelo M. "Hypofunction of the Ovaries." In Nelson Textbook of Pediatrics, edited by Richard Behrman. Philadelphia: W. B. Saunders Co., 1996.
• Hall, Judith G. "Chromosomal Clinical Abnormalities." In Nelson Textbook of Pediatrics, edited by Richard Behrman. Philadelphia: W. B. Saunders Co., 1996.

  Periodicals

• "Health Supervision for Children with Turner Syndrome." Pediatrics, 96 (6)(December 1995): 1166+.
• Saenger, Paul. "Turner's Syndrome." The New England Journal of Medicine, 335 (23)(December 5, 1996): 1749+.

  Organizations

• Turner's Syndrome Society of the United States. 1313 Southeast 5th St., Suite 327, Minneapolis, MN 55414. (800) 365-9944.

Gale Encyclopedia of Medicine. Gale Research, 1999.