Turner syndrome is characterized by an abnormality in the X chromosome. Normally females have two X chromosomes (and males have one X and one Y). In Turner syndrome, females often have only a single X chromosome (this occurs in 60 percent of patients with Turner syndrome).
Turner syndrome occurs in approximately 1 of 2,500 females. About 95 percent of fetuses are spontaneously miscarried during pregnancy and thus only 5 percent survive to term. Most cases of Turner syndrome occur randomly and thus do not carry a recurrence risk.
Since patients with Turner syndrome are unable to have children, there is no risk of mother-daughter transmission. Although most women with Turner syndrome are infertile secondary to abnormal ovary development, there have been case reports of women with Turner syndrome becoming pregnant. Prenatal diagnosis is available through amniocentesis (sampling of the fluid which surrounds the baby before birth) to look for the abnormality of the X chromosome.
Patients may also have “cell line mosaicism”, meaning not all cells in the body have identical chromosomes. Normally all cells have the same chromosomes, but in some patients with Turner syndrome, some cells will have the normal XX pattern and some will have X0 (meaning only one X chromosome as opposed to the normal two chromosomes). There are a number of possible mosaic patterns. If a “Y” cell line is present, the patient is at higher risk for developing a particular type of cancer of the ovary and thus removal of the ovaries is recommended.
Common features of Turner Syndrome include:
- Swelling of the hands and feet. Other features may also be involved, including the head, neck, and arms
- A triangular face with downslanted eyes
- Low set ears that are rotated to the back
- Short neck with skin folds along the side, giving a webbed appearance
- Small upper jaw
- The hairline in the back is low on the neck and may extend onto the back
- Broad chest with nipples that appear small and spaced far apart on the chest wall (a so-called “shield chest deformity”)
- Abnormalities of the arms in the angle of the elbow, and deformities of the fourth and fifth fingers, and underdevelopment of the fingernails and toenails
- Curvature of the spine (scoliosis)
- Multiple moles on the skin
- Growth is delayed and the average adult height is about 4 feet 7 inches
- Infertility and lack of normal pubertal development (e.g., breast and pubic hair) are common. This is due to abnormal development of the ovaries
- Underactive thyroid glands (hypothyroidism)
- Higher risk for tumors arising from neural tissues and also uterine cancer
- Kidney abnormalities including a large single kidney that spans across the abdomen (“horseshoe kidney”) or duplication or malposition of kidney structure or bladder structures
- Average intelligence is normal, although occasional patients will have some degree of mental retardation
Approximately 20 percent of Turner syndrome patients will have a heart defect. The most common problem is coarctation of the aorta, which is a narrowing of the main artery (the aorta) as it carries the red, oxygen-rich blood away from the left side of the heart to the body.
There have been reports of rupture of the aorta in older individuals with Turner syndrome, presumably due to an abnormality in the strength of the aortic wall.
Other common heart defects include:
- A bicuspid aortic valve – two, rather than the normal three leaflets in the valve between the left ventricle and the aorta
- Aortic stenosis – narrowing of the aortic valve
- Atrial septal defect – hole between the upper collecting chambers, or atria, of the heart
Turner syndrome may not be diagnosed until later in life when a girl undergoes medical evaluation for short stature or lack of pubertal development.
Estrogen replacement is usually prescribed at puberty to enhance development of the adult female body but does not restore fertility. Recent advances in the treatment of infertility have made pregnancy possible through the use of a donor egg.
If your child has a heart defect such as coarctation of the aorta, this may require some intervention depending on the degree of narrowing. If the narrowing is mild, nothing may need to be done except regular follow-up with the cardiologist and antibiotics before going to the dentist to prevent infection.
If the narrowing is significant enough to need treatment, this will most commonly require surgery to remove the narrowed segment and reattach the two ends of the aorta together. In some cases treatment for coarctation can be performed in the cardiac catheterization laboratory by dilating the narrowed area with a balloon or putting a stent into the narrowed area.
An atrial septal defect will usually require surgical closure, although selected defects may be amenable to device closure in the cardiac catheterization lab.