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What is Triple X Syndrome?

Triple X syndrome is a genetic disorder that only affects women. It does not always cause symptoms but sometimes it can result in certain physical characteristics/problems, such as taller than average height, a small head, poor motor skills, learning disabilities or behavioral problems and infertility.

Women with triple X syndrome have a third X chromosome in each cell. Sometimes every cell in the body is affected and sometimes only a percentage of cells have three X chromosomes, while the rest have the normal number, i.e. two. This variation between cells is known as mosaicism.

Many women who have triple X syndrome are never diagnosed, partly because it is often symptom-free and partly because if symptoms do occur, there is a wide range/variety of them and they are often mild. This syndrome is thought to affect one in every thousand women. Triple X syndrome is also known as Trisomy X, Triplo X syndrome, XXX syndrome or 47,XXX syndrome.

Fast Facts about Triple X Syndrome

  • Triple X syndrome is a random abnormality of the sex chromosomes, which affects around one in every thousand women
  • It does not run in families
  • Girls born to older women are more likely to have triple X syndrome
  • It may not produce any noticeable symptoms but women who have triple X syndrome are typically taller than average with small heads. There may be mild learning or developmental difficulties, difficulties with motor coordination and behavior problems. If physical symptoms occur, they often relate to fertility
  • There is no treatment for triple X syndrome per se – if treatment is necessary, it is symptomatic, e.g. specialist teaching or counseling for learning or behavioral problems

Causes of Triple X Syndrome

Despite the fact that triple X syndrome is a genetic disorder, it does not run in families. Rather, it is caused by a random malfunction that occurs during the formation of gametes (sperm in men or egg cells in women) from germ cells.

In almost every human cell apart from the gametes, there are 23 pairs of chromosomes. Each of these chromosomes contains genes, strands of DNA that govern our characteristics (hair and eye color, predisposition to certain diseases etc.). One of the pairs of chromosomes determines a person’s gender. In normal healthy women, this pair consists of two X chromosomes, one of which they inherit from their mother and the other from their father. Males have one X and one Y chromosome – they inherit the X chromosome from their mother and the Y chromosome from their father. Thus normal women have the XX chromosome and men have the XY chromosome.

Unlike the rest of the cells in the body, the gametes contain 23 single chromosomes rather than 23 pairs of chromosomes. During fertilization a male sperm cell fuses with a female egg to give a zygote. As part of this process, the chromosomes from the sperm and egg cells join together to give 23 pairs of chromosomes. The zygote then begins dividing to form an embryo/fetus.

To form a gamete, a germ cell undergoes a process known as meiosis, part of which involves splitting of the germ cell’s 23 pairs of chromosomes to form the single strand of chromosomes in the gamete. Sometimes the splitting process fails – the failure to split is known as nondisjunction. When a gamete with an unsplit pair of XX chromosomes fuses with a normal gamete that has a single X chromosome, the resulting zygote has an XXX chromosome. Most cases of triple X syndrome result from fertilization of an XX egg by an X sperm – in other words, most cases of triple X syndrome come from the mother.

In the case of mosaicism (where only some of the body’s cells have an XXX chromosome), the extra X chromosome appears after the embryo has started to develop.

Risk Factors for Triple X Syndrome

By its very nature, triple X syndrome can only affect women, not men. There is some evidence that baby girls born to older mothers are more likely to have triple X syndrome.

Symptoms of Triple X Syndrome

Triple X syndrome may not cause any noticeable symptoms. Girls and women with triple X syndrome are typically taller than average, with a small and/or elongated head and increased spacing between the eyes. There may be reduced muscle tone. Development of speech and language is often slower than normal and the IQ may be a little lower than average. Studies show that girls with triple X syndrome may have short term recall/memory problems, poor motor coordination, behavioral problems and lack of self confidence/social skills.

Occasionally there may also be physical symptoms, often relating to fertility – girls with triple X syndrome are either born infertile or their ovaries cease to function before the age that you would expect menopause to occur. Other symptoms include seizures and kidney problems.

Diagnosing Triple X Syndrome

Triple X syndrome can be diagnosed while the baby is still in the womb via amniocentesis or chorionic villus sampling. After a child is born, a chromosome analysis can be performed on a blood sample.

In many cases, triple X syndrome goes undetected because it frequently produces no physical symptoms and only mild cognitive/behavioral problems, if any.

Treatment Options for Triple X Syndrome

There is no treatment for triple X syndrome itself because it’s not possible to remove the “spare” X chromosome. Any treatment is therefore aimed at helping to correct developmental problems and learning disabilities or physical symptoms if they occur.

Family counseling and psychotherapy may be beneficial in helping children and adolescents with any behavioral and social problems that they are experiencing, by increasing their self-confidence.

Prevention of Triple X Syndrome

Since triple X syndrome is caused by a random chromosomal abnormality, it is not possible to prevent it.

Coping with Triple X Syndrome

Triple X syndrome does not usually cause serious symptoms and most girls who are born with it can go on to lead a normal life.

There are no drug-based or surgical treatments for triple X syndrome but if your child has a mild learning disability and/or problems with motor coordination or behavior as a result of the condition, then they will respond to specialist teaching and counseling. A good point of reference are national centres for learning disabilities that can show you places you can go to for help. You can also talk with your doctor about resources that are available in your area.

Where to Find More Information: The Rare Cromosome Disorder Support Group