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Turner's syndrome

Turner syndrome is a human genetic abnormality, caused by a nondisjunction in the sex chromosomes that occurs in females (1 out of every 2,500 births). Instead of the normal XX sex chromosomes, only one X chromosome is present and fully functional; this is called 45,X or X0. In Turner syndrome, female sexual characteristics are present but underdeveloped. more...

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Symptoms

Common symptoms of Turner syndrome include:

  • Short stature
  • Lymphoedema (swelling) of the hands and feet
  • Broad chest and widely-spaced nipples
  • Low hairline
  • Low-set ears
  • Reproductive sterility

Other symptoms include a small lower jaw, cubitus valgus (turned-out elbows), a webbed neck, and soft, upturned nails. Less common are pigmented moles, hearing loss, and a high-arch palate. Turner syndrome manifests itself differently in different people, and no two women need share the same symptoms.

Causes

Turner syndrome is caused by the loss of genetic material from one of the sex chromosomes. In Turner syndrome, the embryo has only one functioning sex chromosome. This chromosome is always an X chromosome, as an embryo with only a Y chromosome is incapable of survival. The remaining X chromosome is either absent or damaged. Mosaic Turner syndrome, where some of the cells have two sex chromosomes but others have only a single functioning X chromosome, is also possible. In cases of mosaic Turner syndrome, the symptoms are usually less pronounced.

There are no known risk factors for Turner syndrome.

Incidence

Approximately 98% of all fetuses with Turner syndrome spontaneously abort. Fetuses with Turner syndrome make up about 10% of the total number of spontaneously aborted fetuses in the United States. The incidence of Turner syndrome in live births is between 1 in 2,500 and 1 in 3,000.

History

The syndrome is named after Henry Turner, an Oklahoma endocrinologist, who described it in the 1940s. In Europe, it is often called Ullrich-Turner syndrome or even Bonnevie-Ulrich-Turner syndrome to acknowledge that earlier cases had also been described by European doctors.

Diagnosis

Turner syndrome may be diagnosed by an amniocentesis during pregnancy. Sometimes, fetuses with Turner syndrome are identified by abnormal ultrasound findings (i.e. heart defect, kidney abnormality, cystic hygroma, ascities). Although the recurrence risk is not increased, genetic counseling is often recommended for families who have had a pregnancy or child with Turner syndrome.

A blood test, called a karyotype, analyzes the chromosomal composition of the individual. This is the most commonly used blood test to diagnose Turner syndrome.

Medical consequences of Turner syndrome

While most of the symptoms of Turner syndrome are harmless, some can lead to significant medical problems.

Cardiovascular

It is interesting for a better understanding to first consider the results of Price et al, 1986 study of 156 female patients with Turner syndrome. Indeed they showed a significantly greater number of deaths from diseases of the circulatory system than expected, half of them due to congenital heart disease. The interesting finding is that when patients with congenital heart disease were omitted from the sample of the study, the mortality from circulatory disorders was not significantly increased.

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Turner syndrome
From Gale Encyclopedia of Medicine, 4/6/01 by Rosalyn S. Carson-DeWitt

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.

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