Turner Syndrome

September 29, 2011

Turner syndrome (TS), alternately referred to as Turner’s syndrome, monosomy X, and gonadal dysgenesis, was first described in 1938 by Dr. Henry Turner in a case report of several girls with short stature, no secondary sexual characteristics, arms that bent outwards at the elbows (called cubitus valgus), neck webbing, and a low posterior hairline. These characteristics are now recognized as cardinal signs of Turner Syndrome, which occurs in approximately 1/2,000 live female births. There are approximately 60,000 girls and women with Turner Syndrome in the United States; approximately 800 infants are born with Turner Syndrome in the United States every year. All Turner Syndrome children are girls and of short stature, on average 4 ft, 7 in. tall, if not treated with growth hormone. Other signs and symptoms are lymphedema (swelling, often in the hands and feet), a broad chest, a short fourth or fifth metacarpal, low-set ears, a small mandible, strabismus (tendency for eyes to wander or cross), and numerous pigmented nevi (moles). We now understand that there are additional associated abnormalities, including lack of development of the ovaries (ovarian dysgenesis) leading to infertility in the majority of women, curvature of the spine (scoliosis), abnormal bone development (bone dysplasia), inner ear defects, a highly arched palate, kidney malformations, and cardiovascular anomalies (such as a malformed heart [tricuspid] valve, narrowing of the major blood vessel in the chest [aorta], and weakening of the wall of the aorta, which can lead to devastating splitting/tissue breakdown [dissection and rupture]). Other medical complications may include high blood pressure, diabetes, arthritis, obesity, hearing loss, exaggerated scar formation, cataracts, and hypothyroidism. Obtaining health insurance can be difficult for patients with Turner Syndrome; some plans may also refuse to pay for treatments such as growth hormone, as discussed below. Little information about life expectancy exists; current studies are examining this question.

CAUSES OF TURNER SYNDROME

In Turner Syndrome, all or part of one of the X chromosomes is lost near the time of conception. The “pure” form of Turner Syndrome, which was the first form identified and represents approximately 50% of cases, is designated 45X or 45XO, meaning that one of the X chromosomes did not get passed to the child by a parent. “Mosaicism” (approximately 30% of cases) occurs in the developing cell, when cell division fails to properly duplicate the genetic material. In these situations the girl has some cells with the usual number of chromosomes, 46XX, and others that are missing an X. In approximately 20% of girls with Turner Syndrome, both X chromosomes are present, but there are structural abnormalities of one X chromosome. The chromosomal abnormality is not caused by anything either parent has done, and there is no known way to prevent the disorder. Older maternal age is not a factor.

DIAGNOSIS

Only about 1% of pregnancies of Turner Syndrome fetuses result in live births, with spontaneous abortion being the usual consequence of this chromosomal abnormality. Early diagnosis is critical for possible prevention and treatment of the signs and symptoms of Turner Syndrome. The diagnosis is made by chromosomal testing (karyotype), which may be done before birth (prenatally) as part of a specialized procedure to examine the fluid or tissue surrounding the fetus (amniocentesis or chorionic villus sampling procedure). Turner Syndrome may be suspected during ultrasound if the test reveals a heart defect or a specific type of fluid accumulation around the neck (lymphatic fluid). Approximately half of Turner Syndrome girls are diagnosed during infancy due to physical features consistent with the disorder, although many escape detection. Later on, short stature and failure to develop secondary sexual characteristics such as breasts or public hair often indicate a problem. On rare occasions, diagnosis is delayed until adulthood when a woman seeks care for loss of the menstrual period and/or infertility.

TREATMENT

Current recommendations for treatment include use of growth hormone (with or without androgens) to ameliorate short stature, estrogen to initiate the development of secondary sexual characteristics, attention to learning and possible learning disabilities, consideration of social and emotional development, and close medical screening and follow-up of associated medical problems. A specialist in childhood endocrine disorders (pediatric endocrinologist) typically prescribes and directs the hormonal treatment. Growth charting is used to track growth; when the girl’s height drops below the 5th percentile (growth category) on a standard growth chart, growth hormone is usually started. This may be done as early as age 2 years. Treatment with growth hormone may be combined with low-dose hormone treatment (androgens) after the girl has reached the age of 9 years to further aid growth. Estrogen accelerates skeletal maturation, so treatment with this hormone is often delayed until the age of 12-15 years to allow for more growth. Only 1% of girls with Turner Syndrome menstruate without estrogen treatment. Estrogen therapy initiates puberty changes—breast development, uterus growth, and body contour changes. After 1-3 years, the hormone progesterone is added to begin the menstrual cycle. Female hormone therapy is typically continued until around the age of 50 years, when menopause would usually occur.

Girls with Turner Syndrome have a high rate of nonverbal learning disabilities, such as visual-spatial difficulties and trouble with math. Early detection and work with specialists can help the child learn strategies to deal with the deficits, which if left unaddressed can contribute to social difficulties. Attention to the girl’s emotional growth and development is extremely important as she may feel different from other girls due to her slower growth and sexual development. Support groups fill a critical need in this area as girls with Turner Syndrome meet others with the syndrome, and parents receive practical advice and support.

See Also: Access to health care, Health insurance, Hormone replacement therapy

Suggested Reading

  • Ginther, D. W., & Fullwood, H. (1998). Turner syndrome. In L. Phelps (Ed.). Health-related disorders in children and adolescents: A guidebook for understanding and educating (pp. 691-695). Washington, DC: American Psychological Association.
  • Powell, M. P., & Shulte T. (1999). In S. Goldstein & C. R. Reynolds (Eds.), Handbook of neurodevelopmental and genetic disorders in children. New York: Guilford Press.
  • Rosenfeld, R. G. (1992). Turner syndrome: A guide for physicians, Second Edition. Houston, TX: The Turner Syndrome Society.

 

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