The Turner syndrome (sometimes called gonadal dysgenesis ) is a genetic disease that affects only women. The anomaly concerns one of the X chromosomes (the sex chromosomes). Turner’s syndrome affects about 1 in 2,500 women and is often diagnosed several years after birth, at the time of adolescence. The major symptoms are a small size and abnormal functioning of the ovaries. Turner’s syndrome is named after the American doctor who discovered it in 1938, Henri Turner.
Men have 46 chromosomes including two sex chromosomes called XY. The genetic formula of a man is 46 XY. Women also have 46 chromosomes including two sex chromosomes called 46 XX. The genetic formula of a woman is therefore 46 XX. In women with Turner syndrome, the genetic combination contains a single X chromosome and the genetic formula of a woman with Turner syndrome is 45 X0. Either these women lack an X chromosome or it exists, but has an anomaly called deletion. There is always a chromosomal deficiency.
What are the causes of Turner syndrome?
The origin of Turner syndrome is an accidental genetic abnormality. This means that it is not transmitted by the parents, but that there is an accident in the chromosomes. The anomaly can be variable:
- An X chromosome may have completely disappeared, as is the case for 55% of women with Turner syndrome.
- An X chromosome may be present, but be incomplete, that is to say, have lost some of its genetic material. This represents 25% of women with Turner syndrome.
An X chromosome may be missing or incomplete, but only in some cells of the body. The body is then formed of 46XX cells and other 45X0. We talk about mosaicism.
What are the symptoms of Turner’s syndrome?
Turner’s syndrome is characterized by clinical manifestations of varying intensity depending on the lack of genetic material. A completely absent X chromosome causes more symptoms than a small part of the missing X chromosome or a case of mosaicism.
Here are the observable symptoms:
- Small size from birth and even before, but the slowdown in growth compared to other children is especially noticeable from 4 years. The height in adulthood is on average 20 cm less than the average, or 1.45 m.
- The lack of development at the time of puberty, because of abnormalities of the ovaries: the breasts do not develop and the rules do not appear. In some cases, however, rules may appear.
- Infertility is most often present. Only 1 to 2% of women with Turner syndrome may be pregnant.
- There is swelling of the feet and hands at birth.
- The neck is called “webbed”.
- There are deformations at the elbows.
The risks and complications of Turner syndrome
Apart from the symptoms previously mentioned, other pathologies are sometimes associated with Turner syndrome:
- Cardiac or aortic malformation is present in 5% of cases significantly and in 30% of cases, there are minor malformations.
- Arterial hypertension affects 40% of women with Turner syndrome.
- Kidney malformations are present in 30% of cases.
- Osteoporosis (bone disease).
- Hypothyroidism .
- Visual (strabismus) and auditory ( repeated otitis ) disorders .
- The intellectual abilities , which are normal for the majority of women with Turner syndrome, are however reduced in 6% of cases.
Almost all embryos with Turner syndrome (98-99%) undergo spontaneous abortion during the first 3 months. In the United States, it is implicated in 10% of spontaneous miscarriages.
The diagnosis of Turner syndrome
It is not always easy to diagnose Turner syndrome at an early stage.
However, it is sometimes mentioned prenatally on ultrasound anomalies. A sample of amniotic fluid can then allow a certain diagnosis. Turner’s syndrome can also be detected at birth. But most often, it is discovered in adolescence.
The diagnosis is made using a karyotype, which is a chromosome analysis and detects abnormalities present.
Medical treatments for Turner syndrome
The growth hormone is to treat the small size and allows girls with Turner syndrome to achieve greater than 1.50 m height.
An HRT was set up at the time of puberty. It consists of providing the hormones that would normally have been made by the ovaries. This treatment is continued until the age of menopause around 50 years. It does not restore fertility, but it allows a better feminization of the body (breasts) and reduces the risk of osteoporosis. The treatment combines estrogen and progesterone hormones.
Hormonal treatment allows these women to have a normal sex life. Pregnancies are sometimes possible with medical assistance such as oocyte donation and in-vitro fertilization.
A child, a teenager or a young woman with Turner syndrome must be followed by a specialized team because this syndrome affects many areas and medical monitoring must be very rigorous.