A chromosome disorder in which a girl has only one X chromosome
Normally, girls have two copies of the X sex chromosome. In Turner’s syndrome, only one X chromosome is present, giving a total of 45 chromosomes instead of the normal complement of 46. Girls without a second X chromosome have ovaries that do not function normally. As a result, certain hormones that are needed for normal growth and sexual development, such as oestrogen and progesterone, are not produced, leading to infertility. Turner’s syndrome affects about 1 in 2,500 girls in the UK.
Some symptoms of Turner’s syndrome may be present at birth and include:
Puffy hands and feet.
Short, broad neck.
However, in some girls, there may be no symptoms except short stature. In some cases, Turner’s syndrome is recognized only when a girl fails to reach puberty at the normal age (see Abnormal puberty in females). If the condition is recognized and treated before adolescence, a girl is more likely to attain a greater height and will develop normal female sexual characteristics, such as breasts, and have menstrual periods.
About 3 in 10 girls with Turner’s syndrome also has an abnormal narrowing of the aorta, the main artery of the body (see Congenital heart disease). About 1 in 3 girls with Turner’s syndrome has a mild kidney abnormality. Hearing impairment is common and is usually sensorineural (see Hearing loss). Vision problems, including squints, are also common (see Strabismus). In later life, other possible complications include infertility (see Female infertility) and osteoporosis, in which the bones progressively become thin and brittle.
Girls with Turner’s syndrome are of normal intelligence, but some may have minor learning disabilities, especially with respect to mathematics and activities requiring hand–eye coordination. Psychological problems may also arise when a girl becomes aware of her sexual immaturity and short stature.
Turner’s syndrome may be diagnosed in the fetus during routine ultrasound scanning in pregnancy. Antenatal genetic tests can confirm the diagnosis. Most fetuses with severe Turner’s syndrome die before birth. If the fetus survives and the condition is suspected in infancy or childhood due to short stature, a blood test will be carried out to analyse the chromosomes. Mild Turner’s syndrome may not be suspected until adolescence, when puberty and menstruation do not occur.
There is no cure for Turner’s syndrome, and treatment for the disorder is aimed at relieving some of the symptoms. Growth hormone and oestrogen may be given to encourage growth, allow normal puberty, and prevent the early onset of osteoporosis. Growth hormone is usually given only until the child reaches the usual age of puberty. Oestrogen is then given from this age and is continued for life.
Other treatments focus on associated complications. The ears will be checked regularly for fluid build-up. Narrowing of the aorta can be corrected surgically if necessary. Women who have Turner’s syndrome are extremely unlikely to conceive naturally.
Genetic counselling is usually offered to the parents of a daughter with Turner’s syndrome, although the risk of having another affected child is low. Affected individuals and their parents may find it useful to contact a support group.
Although affected girls do not grow to the average height for their age, most should be able to have a normal childhood and eventually to become healthy and independent women. Even serious complications that are associated with Turner’s syndrome, such as a narrowed aorta, can now be treated successfully.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.