Turner syndrome

There are various signs and symptoms of Turner syndrome, which can range from very mild to more severe. Short stature is the most common feature and usually becomes apparent by age 5. In early childhood, frequent middle ear infections are common and can lead to hearing loss in some cases. Most affected girls do not produce the necessary sex hormones for puberty, so they don't have a pubertal growth spurt, start their periods or develop breasts without hormone treatment. While most affected women are infertile, pregnancy is possible with egg donation and assisted reproductive technology. Intelligence is usually normal, but developmental delay, learning disabilities, and/or behavioral problems are sometimes present.

Additional symptoms of Turner syndrome may include:

• a wide, webbed neck
• a low or indistinct hairline in the back of the head
• swelling (lymphedema) of the hands and feet
• broad chest and widely spaced nipples
• arms that turn out slightly at the elbow
• congenital heart defects or heart murmur
• scoliosis (curving of the spine) or other skeletal abnormalities
• kidney problems
• an underactive thyroid gland
• a slightly increased risk to develop diabetes, especially if older or overweight
• osteoporosis due to a lack of estrogen, (usually prevented by hormone replacement therapy).^[1][2]

In Turner syndrome, an individual does not have the usual pair of two complete X chromosomes. The most common scenario is that a girl has only one X chromosome in all of her cells. However, some girls with Turner syndrome have a full or partial absence of the X chromosome in only some of their cells.^[3] When an individual has a different chromosomal content in his/her cells, it is called mosaicism. When some of the cells have one X chromosome and no other X or Y chromosome, and other cells have either the usual two sex chromosomes (two X's or one X and one Y) or other chromosomal differences, it is called mosaic Turner syndrome. Mosaic Turner syndrome, like Turner syndrome, is not typically inherited. It occurs as a random event during cell division in early fetal development. Other sex chromosome abnormalities are also possible in individuals with X chromosome mosaicism.^[4] Mosaicism of both the X and the Y chromosome is a common finding in Turner syndrome.^[5]

The features of mosaic Turner syndrome can vary considerably from individual to individual. In females, they can range from mild to severe signs and symptoms of Turner syndrome. In males, they can range from a seemingly normal male to the presence of a variety of features which can include dysmorphic (abnormally formed) features, mild intellectual disabilities, infertility, Ulrich-Turner stigmata (drooping of upper eyelid, extra “webbing” on the neck), gonadal dysgenesis, infertility, low testosterone levels, and azoospermia (having no sperm).^[6]

The long-term outlook (prognosis) for people with Turner syndrome is typically good. Life expectancy is slightly shorter than average but may be improved by addressing and treating associated chronic illnesses, such as obesity and hypertension.^[7] Regular checkups have shown substantial improvements in the quality and length of life for women with Turner syndrome.^[8] While almost all women are infertile, pregnancy with donor eggs and assisted reproductive technology is possible. Even with growth hormone therapy, most affected people are shorter than average.^[7]

There is wide variation in features that have been reported in individuals with a 45,X/46,XY karyotype (a form of Turner syndrome mosaicism). Studies have reported that 90 percent of individuals diagnosed before birth (prenatally) have normal male appearance at birth, while those diagnosed after birth (postnatally) show a wide spectrum of features, ranging from "classic" Turner syndrome, mixed gonadal dysgenesis (the presence of some male structures as well as a uterus, vagina, and fallopian tubes), and male pseudohermaphroditism (genitalia are of one sex, but some physical characteristics of the other sex are present) to apparently normal male. There may be a risk for late-onset abnormalities, such as testicular problems leading to infertility or cancer, and short stature, which could be improved with growth hormone therapy.^[9] Classic Turner syndrome features seem to be the most common features. Mild intellectual disabilities and signs of autism have also been reported.^[10]

To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by the American College of Medical Genetics and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from Genetics Home Reference.