Turner syndrome is a chromosomal disorder that affects only females. It involves a lack of part or all of a second sex chromosome in some or all cells.

Girls are often short in stature, and they may have some emotional and learning difficulties, but most will have normal intelligence.

Turner syndrome (TS) is also known as Turner's syndrome, 45,X syndrome, Ullrich-Turner syndrome, or Gonadal dysgenesis.

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Turner syndrome is a chromosomal disorder.

People without Turner syndrome have 46 chromosomes, of which two are sex chromosomes. Females have two X chromosomes.

However, individuals with Turner syndrome do not have part of a second sex chromosome. Sometimes the whole chromosome will be absent.

Around 1 in 2,500 girls is born with the condition, but it probably affects more pregnancies that do not survive to term. In the United States, around 70,000 women are thought to have TS.

Life expectancy is slightly lower than it would be for most people.

Chromosomes are strands of deoxyribonucleic acid (DNA) that exist in all the cells of the human body. Chromosomes contain instructions that make a human's behavioral and physical characteristics.

Types

There are two types of Turner syndrome:

  • In classical Turner syndrome, an X chromosome is completely missing. This affects about half of all people with TS.
  • Mosaic Turner syndrome, mosaicism, or Turner mosaicism is where the abnormalities occur only in the X chromosome of some of the body's cells.

The signs and symptoms of Turner syndrome vary considerably. They may even appear before birth.

Signs and symptoms before birth include lymphedema. Lymphedema happens when fluid is not properly transported around the organs of the fetal body, and excess fluid leaks into the surrounding tissue, resulting in swelling.

Newborns with TS may have swollen hands and feet.

The fetus may have:

  • thick neck tissue
  • cystic hygroma, or swelling of the neck
  • lower than normal weight

At birth or during infancy, there may be:

  • a broad chest with widely-spaced nipples
  • cubitus valgus, where arms turn outwards at the elbows
  • drooping eyelids
  • fingernails that turn upward
  • a high, narrow palate, or roof of the mouth
  • low hairline at the back of the head
  • low-set ears
  • small and receding lower jaw
  • short hands
  • slower or delayed growth
  • smaller height and weight at birth
  • swelling of the hands and feet
  • wide neck with extra folds of skin, sometimes described as "web-like"

In some cases, TS may not become apparent until later on.

Later signs and symptoms include:

  • Irregular growth: Growth spurts may not occur at expected childhood times. During the first 3 years of life, the infant may have normal height, but by the age of 3 years, their growth rate will be lower than average, and by the age of 5 years, short stature will be noticeable.
  • Short stature: An adult female may be about 8 inches, or 20 centimeters, shorter than expected for an adult female member of that family, unless they have treatment.

Most girls with TS have normal intelligence and good verbal and reading skills, but some may have problems with math, spatial concepts, memory skills, and fine finger movements.

Social problems include difficulty interpreting other people's reactions or emotions.

Normally, during puberty, a female's ovaries start producing the sex hormones, estrogen, and progesterone. Most girls with TS will not produce these sex hormones.

This leads to:

  • no onset of menstrual periods
  • poorly developed breasts
  • possible infertility

Although a female with TS has non-functioning ovaries and is infertile, her vagina and uterus, or womb, is usually normal, and most females with TS will be able to have a normal sex life.

Around 20 percent of females with TS will start menstruating during puberty, but it is rare for a woman with TS to become pregnant without fertility treatment.

Other possible signs and symptoms include:

  • eyes that slant downwards
  • prominent earlobes
  • mouth abnormalities that can cause dental problems
  • narrowing of the aorta, which may result in a heart murmur
  • hypothyroidism, or an underactive thyroid gland, treatable with thyroxine tablets
  • hypertension or high blood pressure
  • osteoporosis, or brittle bones, due to insufficient estrogen
  • otitis media, middle ear infection, or glue ear, is common among young girls with TS
  • hearing loss in adulthood may be due to otitis media during childhood
  • diabetes is more likely in older and overweight females with TS than in other women with similar weight and age
  • moles may be prevalent on the skin
  • small spoon-shaped nails
  • a fourth finger or toe that is shorter than normal

Most people are born with two sex chromosomes. Males inherit the X chromosome from their mothers and the Y chromosome from their fathers. Females inherit one X chromosome from each parent.

When a female has TS, one X chromosome copy is either absent or significantly altered.

A number of genetic alterations are possible in TS.

Monosomy: One X chromosome is completely missing. Experts believe this is caused by an error either in the father's sperm or the mother's egg. Every cell in the offspring's body has one X chromosome missing.

Mosaic Turner syndrome, also called mosaicism or Turner mosaicism: During the early stages of fetal development, an error may occur in cell division, resulting in some cells having two X chromosome copies, while others only have one. Sometimes, there may be some cells with both X chromosome copies, and others with one altered copy.

Y chromosome material: A small number of people with TS have some cells with just one X chromosome copy, and others with just one X chromosome copy and some Y chromosome material. The individual develops as a female but with a higher risk of developing a type of cancer known as gonadoblastoma.

The loss or abnormality of the X chromosome occurs spontaneously at conception when the egg is fertilized. The missing or altered X chromosome causes errors during fetal development and in development after birth.

Having one child with TS does not increase the risk of having other children with the condition.

Only females are affected.

Risk factors

It is thought that the risk of having TS is the same for all females, regardless of ethnicity or location. It occurs randomly, it is not associated with parental age, and there are no known toxins or environmental factors that appear to affect the risk.

During pregnancy, an ultrasound test may reveal signs of TS. Amniocentesis or chorionic villus sampling (CVS) are antenatal tests that can detect chromosomal abnormalities.

At birth, heart or kidney problems, or swelling of the hands and feet may indicate TS.

If an infant has a wide or webbed neck, a broad chest, and widely spaced nipples, or if, as a girl grows, she has a short stature and undeveloped ovaries, TS may be present.

Sometimes diagnosis does not happen until later, for example, when puberty does not occur.

A karyotype blood test can detect extra or missing chromosomes, chromosomal rearrangements, or chromosomal breaks.

This may be done by taking a sample of the amniotic fluid while the baby is still in the uterus, or by taking a blood sample after birth. If one X chromosome is missing or incomplete, TS is confirmed.

Turner syndrome is a genetic condition with no cure, but treatment may help resolve issues with short stature, sexual development, and learning difficulties.

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Girls with Turner syndrome may be short in stature, but hormone treatment can boost growth.

Early preventive care is important to reduce the risk of complications. Blood pressure and the thyroid gland need frequent monitoring, and any necessary treatment must be given immediately.

Treatment for inner ear infections with an ear nose and throat (ENT) specialist can minimize the risk of hearing difficulties later in life.

Hormone therapy may include estrogen, progesterone, and growth hormones. An endocrinologist or pediatric endocrinologist can provide these.

Growth hormone therapy should start if the girl does not grow normally, to prevent short stature and social stigmatization later in life. A daily injection of growth hormone may add an extra 4 inches, or 10 centimeters, to the girl's eventual stature. The best age to start this has not been confirmed, but treatment commonly starts from the age of 9 years.

Estrogen and progesterone replacement therapy will enable sexual development and reduce the risk of osteoporosis. Blood tests can show how much hormone the patient is producing naturally.

Estrogen replacement therapy will start at the onset of puberty, around 14 years of age, starting with low doses that slowly increase. Progesterone therapy, given later, can trigger menstruation. Sex hormone treatment will continue for the rest of the person's life. It may be given as tablets, injections, or patches. Around 90 percent of girls with Turner syndrome will need hormone treatment to trigger puberty and boost growth.

In-vitro fertilization (IVF) will be necessary if the individual wishes to become pregnant. Any pregnancy will need close monitoring, because of the extra strain on the heart and blood vessels.

Counseling and psychological therapy can help patients with psychological problems.

Learning assistance and educational support can help those who have problems with numeracy, spatial concepts, memory skills, and fine finger movements.

A number of complications are associated with TS.

Cardiovascular problems

Some girls with TS are born with either heart defects or very slight heart abnormalities. These can raise the risk of complications later in life.

Defects in the aorta, the main blood vessel leading out of the heart, increases the risk of aortic dissection, a tear in the inner layer of the aorta.

Any defect in the valve between the aorta and the heart increases the risk of an aortic valve stenosis, or narrowing of the valve. This affects between 5 and 10 percent of people with TS.

High blood pressure, or hypertension, is more likely with TS.

Other problems

Other possible complications include:

Diabetes: This is more likely among older women with TS who are overweight, compared with other women of the same age and weight.

Hearing problems: Gradual loss of nerve function and an inner ear infection can cause hearing loss.

Kidney problems: Around 40 percent of patients with TS have some type of kidney malformation, raising the risk of hypertension and urinary tract infections.

Hypothyroidism: An underactive thyroid gland affects 10 percent of among patients with TS.

Tooth loss: This can result from poor or abnormal tooth development. The shape of the mouth and palate increases the chance of overcrowded and poorly aligned teeth.

Vision: Strabismus and farsightedness, or hyperopia, is more common among girls with TS. In strabismus, the eyes do not work in parallel, and they appear to be looking in different directions.

Bones: There is a higher risk of osteoporosis and kyphosis, or forward rounding of the upper back. Scoliosis, a sideways curvature of the spine, affects about 10 percent of people with TS.

Pregnancy: A woman with TS has a significantly higher risk of developing complications during pregnancy, including gestational diabetes, high blood pressure, and aortic dissection.

Psychology: TS increases the risk of having problems with self-esteem, anxiety, depression, attention deficit hyperactivity disorder (ADHD), and social interaction.

Early intervention increases the chance of solving these problems before they occur.