Turner syndrome
Turner syndrome: understanding this female genetic disease
Turner syndrome is a genetic disease that affects only women, depriving them of a sex chromosome. The main manifestations of the disease are short stature, ovarian dysfunction and infertility. Treatment involves taking sex and growth hormones. Explanations.
Definition: What is Turner syndrome?
Turner syndrome is a chromosomal genetic disorder that affects only women. More specifically, this syndrome is linked to the absence of all or part of one of the two X chromosomes in women.
The disease manifests itself by growth retardation in childhood and then by short stature in adulthood, but also by a malfunction of the ovaries, with infertility in the majority of cases . Other symptoms are sometimes associated: kidney and heart problems and diffuse osteoporosis. Morphological peculiarities in the face and limbs may be present: round face, low implantation of the ears, slightly short neck, numerous moles on the skin, thorax rounded in a widened shield with widely spaced nipples...
It is possible to detect the disease before birth through prenatal screening, especially when ultrasound scans reveal certain abnormalities . But in the majority of cases, Turner syndrome is diagnosed during childhood by growth retardation or at puberty , by the absence of breast development or the absence of periods.
Treatment mainly involves taking growth hormones and estrogen and progesterone. Management of associated disorders is also necessary.
How many women have the syndrome?
Turner syndrome affects 1 in 2,500 women, or nearly 10,000 women. It is actually much more common from conception, but only 2% of affected fetuses reach term. It is therefore the cause of 10% of all spontaneous miscarriages.
What causes Turner syndrome?
Normally, women have two X chromosomes (their genetic formula is written 46,XX). However, women with Turner syndrome have one X chromosome that is completely or partially absent . This chromosomal abnormality occurs accidentally during the conception of the fetus.
- In 55% of cases the absence of an X chromosome is complete. We speak of monosomy X (45,X) .
- In 25% of cases, there are two X chromosomes, one normal, the other present but incomplete: this is called a deletion .
- In 20% of cases, the loss of the X chromosome does not occur in all cells of the body, but only in a few. We are talking about mosaicism . In rare cases of mosaicism, material from a Y chromosome may be present in some cells.
What are the risk factors for Turner syndrome?
No environmental factors involved
The disease is also found in all regions of the world. No population or ethnic group is particularly at risk. Furthermore, no environmental factors, including maternal age ( late pregnancy ) or events during pregnancy, appear to be involved in the occurrence of the disease.
An accidental genetic disease in the majority of cases
Most of the time, monosomy X (i.e. the existence of only one X chromosome instead of two) is accidental and its reappearance during a subsequent pregnancy is unlikely.
On the other hand, some structural anomalies (deletions) can be transmitted by hereditary means but this does not mean that Turner disease is a familial disease. Most often, the affected girl has no family history.
What are the symptoms of Turner syndrome?
Symptoms of Turner syndrome vary greatly from patient to patient. Often, short stature and infertility in adulthood are the only signs of the disease.
Recognizing Turner Syndrome During Pregnancy
Before birth, Turner syndrome can be seen by certain signs that can be detected on ultrasound:
- neck edema (cervical hygroma) sometimes even by generalized edema (hydrops fetalis) . In this case, the risk of miscarriage is high.
- In other cases, there is no edema but a malformation of the heart or kidney, or short stature .
Finally, it happens that there are no manifestations in utero.
Recognizing Turner Syndrome at Birth
In infants, there is usually no other sign than a reduced birth size . However, other manifestations are sometimes associated:
- swelling (edema) of the backs of the hands and feet (Bonnevie-Ulrich syndrome) ;
- upward curved nails ;
- a characteristic webbed neck (pterygium colli) ;
- heart defects : in about 5% of cases a severe heart defect or severe narrowing of the aorta, the main artery leading out of the heart (coarctation of the aorta), must be operated on quickly after delivery.
Recognizing Turner Syndrome in Children
Usually, the diagnosis is made during childhood. Signs include:
- growth retardation (the growth curve shows a progressive slowdown and deviates from the standard curves around the age of 4 years) and short stature present in 98% of cases. Turner syndrome would cause a loss of approximately 20 cm in adulthood. In the absence of treatment, the final height is around 145 cm. The growth curve is characteristic with a progressive slowdown.
- The absence of signs of puberty results from an abnormality in the functioning of the ovaries (ovarian dysgenesis). The girl does not see her breasts develop and does not experience the onset of menstruation. However, in about 25% of cases breasts may appear; in 15% of cases, menstruation begins but generally stops quickly.
Recognizing Turner Syndrome in Adult Women
In adults, women with Turner syndrome may have certain characteristics:
- a small size (usually around 145 cm);
- a face and morphology that are sometimes evocative: round face, low-set ears, short neck, wide thorax, wide nipples, etc.;
- many moles on the skin;
- infertility: however, cases of pregnancy are observed (1 to 2% of patients);
- an absence of signs of femininity (breasts, hips, etc.) in the absence of hormonal treatment;
- orthopedic disorders : congenital dislocation of the hip (hip dysplasia) or lateral deviation of the spine (scoliosis)...
Other organs may be affected:
- the cardiovascular system: heart malformations, premature hypertension, etc.;
- kidneys: single kidney, horseshoe (or U-shaped) kidney, etc.;
- urinary tract (malformations);
- bones: osteoporosis (due to estrogen deficiency);
- the endocrine system: non-insulin-dependent diabetes, poor functioning of the thyroid gland ( hypothyroidism ), obesity, etc.;
- ears: repeated ear infections , reduced hearing (hypoacusis), etc.;
- eyes: strabismus ;
- Learning: Less than 6% of those affected have cognitive impairment related to estrogen deficiency. There are often specific learning difficulties, difficulties in motor coordination, attention and memory.
How to prevent Turner syndrome?
Prevention of the disease's progression involves its early diagnosis and treatment . In addition, before birth, there is the possibility of resorting to prenatal diagnosis in case of ultrasound abnormalities or in case of abnormalities of serum markers in the maternal blood (which raise suspicion of a chromosomal disorder in the fetus).
Prenatal diagnosis consists of studying the karyotype of the fetus after trophoblast biopsy (the embryonic tissue from which the placenta originates) at 12 weeks of amenorrhea or on amniotic cells taken by amniocentesis (puncture of the fluid surrounding the fetus) at 16 weeks.
However, even if the prenatal diagnosis is positive, it is sometimes difficult to obtain more information on the severity of the disorder and the effects. Thus, the decision to terminate the pregnancy is sometimes complex. It requires detailed information for the parents by a geneticist, a pediatric endocrinologist and, if the parents wish, by a psychologist.
How is Turner syndrome diagnosed?
Clinical examination
Turner syndrome may be suspected clinically:
- in the prenatal period thanks to ultrasound scans;
- at birth in a newborn who presents many suggestive signs;
- during childhood or adolescence when the child is stunted or menstruation does not begin at the time of puberty.
Genetic testing
The diagnosis must be confirmed by a "cytogenetic study" also called karyotype . This technique allows to determine the exact number of chromosomes and their structure.
Additional examinations
Patients with Turner syndrome should undergo additional tests to assess their health.
- Hormonal study in adulthood shows low levels of estrogen in the blood.
- Pelvic ultrasound can reveal a particular appearance of the ovaries (in "fibrous bands").
- A heart ultrasound and MRI (echocardiography) are used to check for possible heart problems.
- Other examinations may be carried out: ENT examinations, ophthalmological monitoring, hip X-rays, etc.
What are the treatments for Turner syndrome?
Treatments aim to correct hormonal deficiencies and monitor the progression and possible complications of the disease. Surgery is sometimes necessary in the event of heart or kidney malformation.
Essential hormone treatment
- Treatment of growth retardation with growth hormone begins in childhood.
- At the time of puberty, the supply of ovarian hormones or estrogens initially, then estrogens and progesterone, is essential.
- In adulthood, estrogen and progesterone therapy should be continued. Its discontinuation should only be considered around the presumed age of menopause. In rare cases, when Y chromosome material has been detected in the karyotype, the ovaries should be removed because in these rare cases there is a risk of tumor development.
Treatments for associated disorders
- Heart defects can be treated surgically.
- Orthopedic treatments (surgical and non-surgical) may also be necessary.
- Treatment of possible recurrent ear infections and screening for hearing loss are often performed. Hearing aids may be necessary from childhood.
- Strabismus should be treated early.
- Management of diabetes, hypothyroidism and high blood pressure is essential and should be implemented as early as possible (sometimes from early childhood).
