Genetics Northern California

Turner Syndrome

Turner syndrome is a chromosomal condition that occurs in approximately 1 in 2500 female births. The chromosome finding is called 45,X. The condition was named after Dr. Henry Turner, who, in 1938, described seven young women who had certain features in common. Universal findings of Turner syndrome are short stature and lack of ovarian development. These findings are seen in more than 95% of girls and women with Turner syndrome. Most women with Turner syndrome are infertile. The other classically described physical features are more variable and include a webbed neck and low hairline at the back of the head, arms that turn out slightly at the elbow, and puffiness of the hands and feet at birth. In addition, some girls with Turner syndrome are born with heart or kidney abnormalities.

Intelligence of women and girls with Turner syndrome falls in the same range as that of the general population. There can be some differences in learning styles compared to siblings, with difficulties typically in nonverbal skills and in math and spatial perception. Learning differences can usually be compensated for. Women with Turner syndrome can certainly lead productive, successful lives.

Turner syndrome can occur in any pregnancy to women of any age or ethnic background. It is not known to be associated with any environmental factors or genetic conditions. It appears to be a random occurrence. Unlike many chromosomal conditions, the age of the mother does not increase the chance of having a child with Turner syndrome.

Surprisingly, Turner syndrome (45,X) is present in about 1%-2% of all early pregnancies. Almost all of these pregnancies miscarry, usually during the first trimester of pregnancy. Only 1% of pregnancies with 45,X will continue to a full term delivery.

Cause
Turner syndrome is caused by complete or partial absence of one of the two X chromosomes normally found in women. Typically, people have 46 chromosomes in most of the cells of their body. These chromosomes come in pairs; 22 pairs are numbered and the 23rd pair are called the sex chromosomes, two X's in females and an X and a Y in males. Each chromosome contains hundreds to thousands of genes which tell our bodies how to grow, function, and develop. In Turner syndrome, all or part of one of the X chromosomes is missing.

In most cases of Turner syndrome, there is a single X chromosome and the absence of a second sex chromosome (either an X or a Y). This is referred to as 45,X (or 45,XO) and is found in about 50% of cases. Some cases of Turner Syndrome are called mosaic, which means that there is a mixture of cell types; some with the usual set of 46 and some with a missing sex chromosome. There can be other less common variations as well.

Diagnosis
Turner syndrome may be diagnosed from before birth through adulthood. A chromosome study, either by prenatal testing or by a blood test, can accurately diagnose Turner syndrome. Testing can also show whether the person has full or mosaic Tuner syndrome.

Prenatal ultrasound can sometimes raise concerns about the possibility of Turner syndrome during pregnancy. In order to confirm a diagnosis, cells from the fetus are needed for evaluation. Turner syndrome can be diagnosed prenatally by having CVS or amniocentesis.

After birth, the diagnosis may be suspected when a person has one or more of the common physical features. Some features can be present at birth, such as puffiness of the hands and feet. In childhood, Turner syndrome may be suspected primarily because of slow growth or short stature. Other prominent features presenting in teenage years are delayed puberty and delayed menstruation, and in adult women, infertility.

Treatment/Services
There is no cure for the underlying chromosome difference that causes the features of Turner syndrome. However, there are treatments for some of the medical issues related to Turner syndrome.

Height: Short stature is the most visible feature of Turner syndrome. The average adult height is 4'8". Studies indicate that final height can be improved through daily injections of human growth hormone.

Infertility: Most women with Turner syndrome are infertile, usually due to ovarian failure. However, the uterus is functional, so reproductive technologies such as in-vitro fertilization may be an option.

Heart Defects: Medical treatments or surgery for heart defects associated with Turner Syndrome are available.

RESOURCES

Genetics Home Reference: Turner syndrome - General information about Turner syndrome provided by the National Library of Health. Also includes links to many related sites.

Turner Syndrome Society - Site offers information about Turner syndrome and support for individuals with Turner syndrome and their families.

Sex Chromosome Problems Discovered Through Prenatal Diagnosis: Turner Syndrome 45,X (pdf) - Booklet developed by The Pacific Norwest Regional Genetics Group to provide families with information about Turner syndrome following a diagnosis from prenatal testing (CVS or amniocentesis).