Síndrome de Turner

What is Turner syndrome?

Turner syndrome (TS) only occurs in females and is present from the time of conception. It describes a set of features which occur when a female has only one complete X chromosome in each cell. The second X chromosome may be missing entirely or may be incomplete. See below to read more about chromosomes and the abnormality present in Turner syndrome.

Turner syndrome is a genetic condition. This means that there is an abnormality with the genes of the affected person. Genes are passed on to a child from each parent, in structures called chromosomes.

You have 23 pairs of chromosomes in each cell of your body. That is, a total of 46 chromosomes. Each chromosome contains thousands of genes. Our genes determine how our body functions, what we look like and sometimes what diseases we will get. The genes that control which sex (gender) we become are part of the chromosomes called sex chromosomes. These can be either X or Y chromosomes. We get one sex chromosome from each parent.

Usually, a female has two copies of the X chromosome and a male has one X and one Y chromosome. An individual's complete set of chromosomes is known as their karyotype. So the karyotype of most women is said to be 46,XX and the karyotype of most men is said to be 46,XY.

Turner syndrome chromosomes

Girls and women with Turner syndrome have only one X chromosome. The karyotype is therefore said to be 45,X or 45,XO.

Turner syndrome occurs in about one in 2,000 live female births. There are no known risk factors for Turner syndrome. It is not more common in girls born to older women and it is very rare to have a second child with Turner syndrome.

Turner syndrome features that may develop before birth are thickness of the neck tissue, a neck swelling called a cystic hygroma, or being a small-sized baby.

Newborn babies with Turner syndrome may have lymphoedema of the hands and feet and excess skin of the neck.

As girls become older, a range offeatures may develop. The following are some of the more common:

Short stature

Most girls with Turner syndrome will be short for their age.

Typical facial features

This may include characteristic changes to the eyes, ears, mouth and neck - for example:

• Downslanting eyes.

• Droopy eyelids.

• Prominent earlobes.

• Crowding of the teeth.

• A short webbed-like neck.

Bone features

Por ejemplo:

• A broad chest with widely spaced nipples.

• A wide carrying angle (this is the angle between the forearm and the hip when the arm is held by the side).

• Short fingers.

• Nail changes.

Características de la piel

Girls with Turner syndrome often have a lot of moles and obvious blood vessels over the skin.

The medical symptoms of Turner syndrome will vary depending on the age of the girl or woman.

Before a girl with Turner syndrome is born, she may have a problem called linfedema. This occurs when fluid is not able to be transported around the body and organs properly. So, some fluid leaks into tissues and causes swelling.

The following symptoms can occur in Turner syndrome:

Susceptibility to certain medical conditions

People with Turner syndrome are more likely to develop certain conditions such as:

• Diabetes mellitus.

• Enfermedad celíaca.

• Una glándula tiroides hiperactiva (hipertiroidismo).

• Inflammatory bowel diseases.

Organ abnormalities

For example, about half will have an abnormality with the heart or major blood vessels. Up to 6 in 10 will have an abnormality of the kidneys or urinary tract.

Ovarian abnormalities

The ovaries are a pair of glands that lie on either side of the womb (uterus). Each ovary is about the size of a large marble. The ovaries normally make eggs (ova) and various female hormones - in particular, oestrogen. Almost all girls with Turner syndrome have ovaries that do not work properly. As a result, they

• May not go through puberty.

• May have breasts which do not develop properly.

• May not ever get a period, and are likely to be infertile. However, up to 3 in 10 girls will have some changes of puberty and 1 in 200 may be able to get pregnant naturally.

Nota: although there are often problems with ovaries, women with Turner syndrome still have a normal vagina and womb and can have a normal sex life.

Síndrome de Turner

© Johannes Nielsen (own work),via Wikimedia Commons

Turner syndrome may lead to the development of secondary abnormalities. The most common are as follows:

Heart and blood vessel complications.

Heart valves may become faulty, abnormalities on the heart tracing (electrocardiogram, or ECG), or abnormalities of the main blood vessels such as the main artery that takes blood from the heart (may develop an aneurysm of the aorta). In some cases the aorta can rupture.

Presión arterial alta is also quite common in Turner syndrome.

Urinary abnormalities

Extra tubes from the kidney to the bladder, only one kidney developing, or unusually shaped kidneys. These abnormalities can make urinary tract infections (urine infections) occur more commonly than usual.

Problemas oculares

About 8 in 100 girls with Turner syndrome have colour vision problems and may develop poor vision over time.

Problemas de oído

Hearing impairment is common and can be due to persistent (chronic) ear infections or deterioration of the nerves.

'Thinning' of the bones

This is also known as osteoporosis. It may occur later in life as a complication of a lack of oestrogen if oestrogen treatment is not started early enough or taken continuously.

Secondary conditions

About 1 in 4 girls with Turner syndrome develop problemas de tiroides. A small number develop coeliac disease, which is a problem with the gut due to an intolerance to gluten.

Turner syndrome may be suspected by your doctor if a girl has some of the above features. The diagnosis can be confirmed by a test called karyotype testing. This involves a sample being taken either from the amniotic fluid around a baby in the womb (uterus), or from a blood sample in children.

The chromosomes can be studied from the sample. When the chromosomes are studied, if there is one X chromosome missing or if it is incomplete in certain parts, this confirms the diagnosis of Turner syndrome.

Can Turner syndrome be detected before birth?

Turner syndrome can be diagnosed before a baby is born, using a test called amniocentesis. Turner syndrome may also be suspected during pregnancy on a routine ultrasound scan if the scan shows any problems with the heart or kidney that are typical of Turner syndrome.

Because there are a number of possible complications of Turner syndrome, certain tests are usually done to diagnose Turner syndrome. Some other tests are then done on a regular basis, sometimes yearly for the rest of your life. The tests include the following:

Análisis de sangre

These include a yearly check of función tiroidea, la función hepática, colesterol y glucose levels. Every 2-4 years, a blood test for coeliac disease is also advised. A blood test for female hormones may also be done to assess whether the ovaries are working or not.

Hearing assessment

A hearing assessment needs to be done at diagnosis and then every 1-5 years depending on the detection of any hearing loss. If frequent ear infections develop, a specialist review and further treatment may be needed.

Vision testing

This needs to be done at least at the time of diagnosis or at age 1 year, whichever is later, and then repeated as required depending on the issues involved.

Heart check

This is usually done by a heart specialist (cardiologist) and includes tests such as an ultrasound of the heart (echocardiogram), blood pressure check, tracing of the electrical activity of the heart (electrocardiogram, or ECG) y MRI scan of the heart. Some of these tests will need to be done regularly and some will only be required a few times.

It is also very important to have regular monitoring of the size of the aorta, which is the main blood vessel in the body. In some girls with Turner syndrome, this blood vessel becomes wider over time and can burst suddenly (rupture) which may be life-threatening. If the size of the main artery that takes blood from the heart (the aorta) is monitored, appropriate treatment, including surgery, can be given to prevent the aorta from bursting.

Kidney check

An ultrasound scan of the kidneys is usually done when Turner syndrome is diagnosed, to assess for abnormalities with the kidneys and urinary tract.

Bone assessments

For young children with Turner syndrome this will mean testing by the doctor for hip dislocations. Teenagers need to be assessed for a curvature of the spine (scoliosis). Bone density scans to check for osteoporosis are also advised.

Weight and exercise

Encourage children with Turner syndrome to comer saludablemente y haz ejercicio regularmente in order to keep weight in the healthy range. This is important because of the increased risk of diabetes and heart problems in Turner syndrome which are more common in overweight people.

Dental check

Due to the small size of the mouth in some girls with Turner syndrome, regular dental checks are advised to manage problems with tooth abnormalities. The most common is a problem with dental occlusion - that is, the way the teeth meet when they bite together.

As this is a condition caused by abnormal genes, there is no cure for it.

There are several effective treatments for different aspects of the syndrome which aim to minimise the impact of the condition. These can be divided into medication treatments (such as hormonal therapy) and non-medication treatments (such as psychological therapy).

The most important medication treatments are:

Hormona de crecimiento

This is sometimes started as early as 12-24 months of age. It should definitely be started as soon as it is clear that a child is not growing normally due to Turner syndrome.

Growth hormone replacement therapy has been shown to increase the final height by as much as 10 cm.

Growth hormone therapy is generally continued until a child reaches a bone age of 14. This means that her bones are the same as the bones of a child without Turner syndrome at age 14.

Oestrogen and progesterone

A blood test for these female hormones can indicate if the ovaries are not working and are not producing enough oestrogen. Oestrogen can be given as a tablet, patch or injection. In this type of hormone replacement therapy, the dose is gradually increased over a few years until a dose is obtained that will give normal oestrogen levels.

Progestogen is added later than oestrogen to help to produce withdrawal bleeds (like periods). These hormone treatments are usually continued throughout life.

Various treatments may be needed and include the following:

Psychological therapy

This can be important for a number of girls and women with Turner syndrome. For example, they may have low self-esteem due to their appearance, or their social functioning or because they are infertile.

Sex education

A small number of girls with Turner syndrome will be able to get pregnant naturally. So, if you have Turner syndrome and are sexually active, as with any other female, you need to be informed about contraception and safe sex practices.

Infertilidad

While a small number of women with Turner syndrome will be able to get pregnant naturally, the vast majority will be infertile. Assisted conception using various forms of IVF may be successful. Regular heart checks before and during pregnancy are essential, as pregnancy increases the strain on the heart and blood vessels.

Learning difficulties

A few girls with Turner syndrome also have learning problems and so specialised assistance with schooling can help to manage this. However, most girls with Turner syndrome have normal intelligence.

Management of lymphoedema

Physiotherapy and support stockings can help to reduce the swelling experienced by some girls with Turner syndrome.

When they become adults, most girls with Turner syndrome will be shorter than average and infertile. However, the development of growth hormone treatment has improved the expected adult height for those treated. The most significant risk faced is that of heart and blood vessel problems. But, regular checks and treatment where necessary have reduced the impact of these complications. Overall:

• Life expectancy is only slightly reduced and quality of life is usually normal.

• Most girls with Turner syndrome have normal intelligence.

• Most have the potential to lead happy and full lives.

As above, many women with Turner syndrome will be unable to become pregnant naturally. A small number may do so, however, and others may be able to become pregnant with treatments such as in vitro fertilisation (IVF). However, this should be discussed at length with a specialist doctor, because pregnancy may be more risky for women with Turner syndrome.

This is due to the susceptibility to other medical problems - for example, heart defects. When the heart is put under more pressure due to pregnancy, it can be dangerous. Each woman should be screened for their individual risks, so they can weigh up the pros and cons of pregnancy. This needs specialist help and expertise.