Laboratory Testing

Most cases of Turner syndrome are not inherited. When this condition results from monosomy X, the chromosomal abnormality occurs as a random event during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may lose a sex chromosome as a result of nondisjunction. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have a single X chromosome in each cell and will be missing the other sex chromosome.

Mosaic Turner syndrome is also not inherited. It occurs as a random event during cell division in early fetal development. As a result, some of an affected person's cells have the usual two sex chromosomes (either two X chromosomes or one X chromosome and one Y chromosome), and other cells have only one copy of the X chromosome. Other sex chromosome abnormalities are also possible in females with X chromosome mosaicism.Turner syndrome (TS) is a medical disorder that affects about 1 in every 2,500 girls. Although researchers don't know exactly what causes Turner syndrome, they do know that it's the result of a problem with a girl's chromosomes.

Most girls are born with two X chromosomes, but girls with Turner syndrome are born with only one X chromosome or they are missing part of one X chromosome. The effects of the condition vary widely among girls with Turner syndrome. It all depends on how many of the body's cells are affected by the changes to the X chromosome.

Girls with Turner syndrome are usually short in height. Girls with Turner syndrome who aren't treated for short stature reach an average height of about 4 feet 7 inches (1.4 meters). The good news is that when Turner syndrome is diagnosed while a girl is still growing, she can be treated with growth hormones to help her grow taller.

In addition to growth problems, Turner syndrome prevents the ovaries from developing properly, which affects a girl's sexual development and the ability to have children. Because the ovaries are responsible for making the hormones that control breast growth and menstruation, most girls with Turner syndrome will not go through all of the changes associated with puberty unless they get treatment for the condition. Nearly all girls with Turner syndrome will be infertile, or unable to become pregnant on their own.

A number of other health problems occur more often in girls with Turner syndrome, including kidney problems, high blood pressure, heart problems, overweight, hearing difficulties, diabetes, and thyroid problems. Some girls with the condition may experience learning difficulties, particularly in math. Many have a difficult time with tasks that require skills such as map reading or visual organization.

In addition to short stature and lack of sexual development, some of the other physical features commonly seen in girls with Turner syndrome are:

• a "webbed" neck (extra folds of skin extending from the tops of the shoulders to the sides of the neck)
• a low hairline at the back of the neck
• drooping of the eyelids
• differently shaped ears that are set lower on the sides of the head than usual
• abnormal bone development (especially the bones of the hands and elbows)
• a larger than usual number of moles on the skin
• edema or extra fluid in the hands and