Alternative names
Bonnevie-Ullrich syndrome; Gonadal dysgenesis; Monosomy X

Definition

Turner syndrome is a birth defect caused by the absence of an X chromosome in some or all cells of a female, which inhibits sexual development and usually causes infertility.

Causes, incidence, and risk factors

A person’s sex is determined by two chromosomes, the X and the Y. Usually, men have an X and a Y, while women have two X’s. In Turner syndrome, a baby girl develops with only one X chromosome. The incidence is 1 out of 3,000 live births.

Turner syndrome usually occurs sporadically, which means that the mutation occurs in fetal development and is not inherited from either parent. In rare cases, a parent silently carries rearranged chromosomes that can result in Turner syndrome in a daughter; this is the only situation in which Turner syndrome is inherited.

Girls with Turner syndrome usually have short stature, webbing of the skin of the neck, absent or retarded development of secondary sexual characteristics at puberty, absence of menstruation, coarctation (narrowing) of the aorta, bicuspid aortic valve, and abnormalities of the eyes and bones. The condition is either diagnosed at birth because of the associated anomalies, or at puberty when there is absent or delayed menses and delayed development of normal secondary sexual characteristics.

IQ is generally normal although some children have learning difficulties. More than half of all patients with Turner syndrome are mosaics, which means that the mutation occurs in some but not all of the cells of their body. This means that it can vary in severity since the fewer cells affected, the more mild the disease will be.

Symptoms

 
• Short stature  
• Webbed neck  
• Abnormal eye features (drooping eyelids)  
• Abnormal bone development, such as a “shield-shaped”, broad, flat chest  
• Absent or retarded development of secondary sexual characteristics that normally appear at puberty, including sparse pubic hair and small breasts  
• Infertility  
• Dry eyes  
• Absent menstruation  
• Absence of normal moisture in vagina; painful intercourse

Signs and tests
During a physical examination, the doctor will look for signs of underdeveloped breasts and genitalia, webbed neck, short stature, low hairline in back, simian crease (a single crease in the palm), and abnormal development of the chest. Infants with Turner syndrome often have swelling of the hands and feet, probably reflecting changes in drainage in the lymphatic system.

 
• Karyotyping shows 45 chromosomes with a pattern 45 X,0 (i.e., a missing sex chromosome).  
• Ultrasound may reveal small or underdeveloped female reproductive organs.  
• A kidney ultrasound can evaluate kidney abnormalities.  
• A gynecologic exam may reveal dry vaginal lining.  
• Serum luteinizing hormone is elevated.  
• Serum follicle stimulating hormone is elevated.  
• Echocardiogram (heart ultrasound) and MRI of the chest are frequently performed after the diagnosis is made to evaluate possible cardiac defects.

This disease may also alter the results of the following tests:

 
• estriol - urine  
• estriol - serum  
• estradiol

Treatment

Growth hormone replacement may or may not be prescribed; it may help the child to achieve a more “normal” height.

Estrogen therapy is started at 12 or 13 years old to stimulate the development of secondary sexual characteristics so that girls affected with this disorder will have a more normal appearance as an adult. Estrogen therapy, however, will not reverse infertility. Vaginal lubricants may prevent dryness, itching, and pain during intercourse.

Cardiac surgery is sometimes necessary to correct heart defects. Antibiotics are recommended for patients with certain types of heart abnormalities in order to prevent infection.

Support Groups
The Turner Syndrome Society of the U.S. is located at 14450 T.C. Jester, Suite 260
Houston, Texas 77014, USA. Call 800-365-9944.

Expectations (prognosis)

This chromosome abnormality is associated with numerous medical conditions and problems in addition to the lack of sexual maturity. In the absence of severe heart defects at birth, most girls with Turner syndrome survive into adulthood and have normal intelligence.

Psychological problems may result from the stigma associated with the condition and its symptoms.

About 2-5% of women with Turner syndrome have some ovarian function. They may spontaneously start menstruating and can then become pregnant. Women with Turner syndrome can also have children using donor eggs and in vitro fertilization.

Complications

 
• Kidney abnormalities  
• High blood pressure  
• Obesity  
• Diabetes mellitus  
• Hashimoto’s thyroiditis  
• Cataracts  
• Arthritis  
• Scoliosis (in adolescence)  
• Middle ear infections are common if eustachian tube abnormalities are present

Calling your health care provider
Call for an appointment with your health care provider if you or your infant appears to have symptoms of this disorder; or if an adolescent girl’s development seems to be delayed. Genetic counseling is strongly recommended. This both provides an explanation of how the missing chromosome causes Turner syndrome and can determine if the disease was inherited or not.

Prevention
There is no known prevention for this inherited disorder. If prenatal amniocentesis karyotype (chromosome analysis) detects a missing X chromosome, signifying Turner syndrome, some parents may wish to pursue genetic counseling.