What it is and how it is treated

Turner syndrome is a chromosomal condition involving a person’s sex chromosomes. Turner syndrome occurs when one of the X chromosomes (sex chromosomes) is missing or partially missing after conception.

In mosaic Turner syndrome, an X chromosome is missing from some cells in people who are designated female at birth.

Keep reading to learn more about the causes of mosaic Turner syndrome, possible symptoms, and available treatments.

Chromosomes are what carry genetic information (also called DNA) from every cell throughout the human body. Each person is born with 23 pairs of chromosomes – 46 in total – including one pair of sex chromosomes, X and Y.

Turner syndrome affects people who were assigned female at birth. While people designated female at birth usually have two X chromosomes (XX), people with Turner syndrome have only one X chromosome.

Because so much genetic information is missing at such an early stage of development, Turner syndrome can lead to a variety of medical and developmental problems, including failure to develop the ovaries, heart defects, and short stature.

There are two main types of Turner syndrome:

  • Turner monosomy X syndrome: This type is defined as a complete loss of the second X chromosome.
  • Turner mosaic syndrome: This type is defined as a partial loss of the second X chromosome.

In general, the symptoms of people with mosaic Turner syndrome tend to be less severe than the symptoms of people with full Turner syndrome. Indeed, the number of cells affected by the missing or deficient X chromosome is lower with mosaicism.

Some cells contain the usual two XX chromosomes and therefore do not contribute to health problems.

Symptoms can vary greatly between people with mosaic Turner syndrome. Some people may not even realize they have this condition until puberty or later in life.

Symptoms can include:

In addition to these symptoms, a person with mosaic Turner syndrome may exhibit certain physical characteristics, including:

  • low hairline at the back of the head
  • narrow, upturned fingernails
  • strap skin on the neck
  • large “shield” chest with wide nipples
  • swollen hands and feet (lymphedema)
  • pigmented moles (nevi)

Again, these symptoms may be milder than those experienced by people with full Turner syndrome. A study 2018 found that people with mosaic (partial) form tended to be closer to average height with fewer reproductive and heart problems.

Turner syndrome is rare. It affects approximately 1 in 2,000 to 2,500 female births worldwide.

The mosaic form of this condition is caused by a partial loss of the second X chromosome. The monochromosomal form is caused by a complete loss of the second X chromosome.

A 2013 study found that between 30% and 40% of people with Turner syndrome have the mosaic form.

The causes of the loss of this second sex chromosome are not yet fully understood. Researchers think it can happen randomly during breeding. This can happen soon after the sperm meets the egg or early in fetal development.

Turner syndrome does not appear to be inherited. That means it doesn’t run in families.

Diagnosis is often made after a baby is born, in childhood or adolescence. The physical characteristics of infants with Turner syndrome may be recognizable at birth or emerge during infancy.

If your child has signs after birth, their pediatrician may order tests, such as:

  • Blood tests to examine chromosomes: Chromosome tests like karyotyping are used to determine if any chromosomes or chromosomal material are missing or altered.
  • MRI: MRIs produce images that can be used to detect heart, liver or kidney problems.
  • Cardiac test: Tests like the echocardiogram can be used to assess heart problems.
  • Ear, nose and throat (ENT) examinations: These tests can help detect hearing problems.
  • Other tests: Tests such as thyroid function tests, liver function tests, and screening for high blood pressure can be used to help diagnose conditions that affect organs or systems in the body.

Prenatal diagnosis (during pregnancy)

In some cases, a doctor can diagnose Turner syndrome before a baby is born through prenatal genetic testing. In particular, karyotyping can be done by taking blood, bone marrow, or other tissues from the mother that can identify any chromosomal abnormalities in the fetus.

Ultrasound can also help doctors diagnose Turner syndrome during pregnancy. Some babies may have lymphedema (swelling) or kidney or heart problems that show up on prenatal ultrasounds.

There is no cure for Turner syndrome. Instead, treatment aims to address any signs or symptoms that a person with Turner syndrome experiences. Treatment varies by person and their needs.

A study 2018 involving people with mosaic Turner syndrome revealed that treatment may not be necessary, particularly in cases where the syndrome is discovered by chance.

This means that some people may have Mosaic Turner Syndrome which does not cause symptoms or health problems, so no treatment is needed.

Otherwise, treatment options may include:

  • Growth hormone therapy: Growth hormone therapy can help treat short stature.
  • Estrogen or progesterone hormone therapy: Hormone therapy, such as estrogen or progesterone therapy, can help improve sexual development.
  • Psychological support: Psychological support, such as cognitive behavioral therapy and other types of counseling, can help deal with depression, stress, or learning problems that people with Turner syndrome may experience.

Symptoms of Mosaic Turner Syndrome tend to be softer than those with full Turner syndrome. As a result, people with this condition can lead relatively healthy lives.

Early diagnosis and treatment can help address growth and development issues before and during puberty. That said, not everyone with Mosaic Turner Syndrome will have developmental delay. Or if they do, these issues may be only minor.

Do people with Mosaic Turner syndrome have fertility difficulties?

Most people with Turner mosaic have either reduced fertility or infertility. In vitro fertilization can help solve fertility problems.

However, people with mosaic Turner syndrome who become pregnant are at risk for blood pressure complications, which can lead to premature birth or fetal growth retardation.

Pregnancy in people with mosaic Turner syndrome is also associated with an increased risk of maternal complications, including heart conditions such as aortic dissection and aortic rupture.

Is there a relationship between mosaic Turner syndrome and autism?

Researchers explore the potential link between Turner syndrome and autism. In a 2018 UK study, the rate of autism in people with Turner syndrome was 21% compared to the UK rate in women of 0.3%.

Mosaic Turner syndrome is a developmental abnormality involving the sex chromosomes. Turner syndrome occurs when one of the X chromosomes (sex chromosomes) is missing or partially missing after conception.

Treatment can help with a person’s specific health issues, but may not be necessary if symptoms are mild.

People with this disease can have a range of health and developmental problems, but they can generally lead healthy lives.

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