Information on the following diseases can be found in the Related Disorders section of this report:

• Noonan Syndrome

The sexual organs of infants with Turner syndrome appear normal at birth. However, they do not experience the physical changes associated with puberty or the normal development of female secondary sexual characteristics. The breasts of affected females do not develop, and they do not begin to menstruate (primary amenorrhea). Pubic and underarm hair (axillary) also fail to appear. These characteristics do not develop due to immature (streak) ovaries that do not produce the female hormone estrogen.

Children with Turner syndrome grow slowly, and affected adults are usually less than 5 feet tall. Intellectual abilities are usually normal. Some people may experience difficulties with visual-spatial relationships (e.g., right-left disorientation) and/or hearing impairment.

Physical malformations are usually apparent at birth and may include an abnormally small, low jaw (mandible), a broad chest, and/or a low hairline. Other symptoms may include swelling of the hands and feet (lymphedema), droopy eyelids (ptosis), and/or abnormally prominent ears. The roof of the mouth (palate) may be very narrow and highly arched in some infants. There may be loose skin folds, webbing, and/or a low hairline at the back of the neck.

Defects in the heart may also occur in infants with Turner syndrome. These may include constriction of the large artery of the heart (aortic coarctation) and other abnormalities of the left side of the heart. Defects that may occur in the urinary system include abnormally shaped kidneys (horseshoe kidney) and an extra set of tubes that carry urine from the kidneys to the bladder (ureters).

Some people with Turner syndrome may have less severe symptoms or physical abnormalities based on the specific genetic defect.

Turner syndrome is a rare chromosomal disorder that occurs in females due to the absence of or defects in one X chromosome. Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Normally, pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males, and two X chromosomes for females.

A genetic test (karyotyping) shows that one X chromosome is missing (45,X) in approximately 50 percent of females with Turner syndrome. Research studies suggest that in approximately 40 percent of these cases, affected females may have some Y chromosomal material in addition to the one X chromosome. In about 30 to 40 percent of affected individuals, some cells contain two X chromosomes, while others do not (mosaicism 45,X/46,XX). In the remainder of cases, the second X chromosome may be present but may show a variety of abnormalities (isochromosomes, deletions, rings, etc.). Although the exact cause of Turner syndrome is not known, it is believed that the disorder may result from an error during the division (meiosis) of a parent sex cells.

Turner syndrome is a rare disorder that affects only females and occurs in approximately 1 in 2,500 female live births in the United States.

Symptoms of the following disorders can be similar to those of Turner syndrome. Comparisons may be useful for a differential diagnosis:

Noonan syndrome is a rare genetic disorder characterized by congenital heart defects, short stature, a broad or webbed neck, and/or droopy eyelids (ptosis). The most common heart defects associated with this disorder include narrowing of the pulmonary valves or atrial septal defects. Noonan syndrome can affect males and females. Children with this disorder also have characteristic facial features that may include widely spaced eyes (ocular hypertelorism), abnormally spaced ears, underdevelopment of the jaw (micrognathia), and/or a vertical fold of skin over the inner corners of the eyes (epicanthus). (For more information on this disorder, choose "Noonan" as your search term in the Rare Disease Database.)

The diagnosis of Turner syndrome is made by a blood test that examines the chromosomes under a microscope (karyotyping) and detects a missing or abnormal X chromosome.

There is no cure for Turner syndrome, but certain therapies can improve physical development. Estrogen therapy, in the form of estradiol (a powerful form of estrogen), may be started early in life to help stimulate and maintain female secondary sex characteristics.

Recombinant human growth hormone (genetically engineered hGH) may promote linear growth in many people with Turner syndrome. Human growth hormone may be given alone or in combination with a steroid drug (i.e., prednisone). The drug is usually started around the age of 7 and continued through the age of 16 or 17 when full adult height is reached in females.

The growth hormones somatropin (Humatrope) and somatropin for injection (Nutropin) have been approved by the U.S. Food and Drug Administration (FDA) for the treatment of short statue associated with Turner syndrome. For information on Humatrope, contact Eli Lilly and Company. For information on Nutropin, contact Genentech, Inc.

Estrogen replacement therapy (a female hormone) may also be initiated around the age of puberty. This generally promotes near normal development of breasts, labia, vagina, uterus, and fallopian tubes. Individuals remain unable to conceive children (infertile). In vitro fertilization (IVF) with a donor egg and an implanted pregnancy is sometimes possible in women with Turner syndrome.

People with Turner syndrome who have mosaics of the X chromosome (i.e., only some cells have abnormal sex chromosomes) may be prone to ovarian tumors. Such people are likely to develop male secondary sexual characteristics (virilization) and have "streak ovaries." These underdeveloped ovaries are located within the connective tissue of the abdomen and should be surgically removed. Hormone therapy may enable some women with this type of Turner syndrome to become pregnant.

Affected females who have Y chromosomal material may also be prone to ovarian tumors and virilization. These individuals should be closely monitored to assess such risk and ensure they receive appropriate treatment.

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.

For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov

The XXYY Project is sponsoring a research study to examine the similarities and unique aspects of all forms of sex chromosome abnormalities. The one-year project, beginning in July 2004, will be conducted at the Children's Hospital in Denver, Colorado, and the UC Davis MIND Institute in Sacramento. Its purpose is to document and publish the medical and psychological differences among all sex chromosome anomalies. For information, contact:

Renee Beauregard
www.xxyysyndrome.org
Phone: (303) 400-3456
Toll Free: (888) 503-3456
info@xxyysyndrome.org

Ethinyl estradiol (EE), an experimental female hormone manufactured by Gynex, may be administered in small doses and may stimulate the development of secondary sexual characteristics in people affected by Turner syndrome. There may also be an increase in the predicted adult height without advancement of bone age. Further studies are necessary to determine the optimal dose and duration of ethinyl estradiol therapy necessary to achieve the greatest adult height in patients with Turner syndrome.

Oxandrolone (Oxandrin) is an experimental oral drug being tested on females with Turner syndrome to increase their linear growth. Oxandrin, manufactured by Bio-Technology General Corp., is available from Quantum Health Resources. For more information, call (800) 741-2698. More studies are needed to determine the long-term safety and effectiveness of this drug for the treatment of Turner syndrome.

Other researchers are studying a combination therapy of oxandrolone and human growth hormone (Humatrope) for people with Turner syndrome. More studies are required to determine the overall effect of this drug combination on increasing growth rate and adult height. This research is sponsored by the National Institute of Child Health and Human Development (NICHD) of the National Institutes of Health. For information, contact the NIH Patient Recruitment Office listed above.

The NICHD is also sponsoring a study called Turner Syndrome: Genotype and Phenotype to examine the clinical and genetic factors related to Turner syndrome. Females seven years of age or older with X chromosome defets may be eligible for this study, which requires a three- to five-day inpatient stay at the National Institutes of Health Clinical Center in Bethesda. For information, contact the NIH Patient Recruitment Office.

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