Triple X syndrome, also known as Trisomy X, 47,XXX aneuploidy, and Triplo-X, XXX Syndrome is a chromosomal abnormality that affects approximately 1 in every 1,000 females. A healthy female has two X chromosomes, one from her father and one from her mother. A female with triple-X syndrome has three X chromosomes.
According to the NIH (National Institutes of Health), USA, 5 to 10 girls with triple X syndrome are born in the USA each day.
A female with triple-X syndrome does not inherit it from her parents. The syndrome generally results from a mistake in the formation of the father's sperm cell or the mother's egg. In some cases triple-X syndrome may be the result of something that went wrong in the development of the embryo.
A girl with triple X syndrome may either have no symptoms, just mild ones, or more severe ones with developmental delays. Developmental delays may include learning disabilities, delayed development of speech and language skills, as well as motor skills. There may be behavioral and emotional difficulties. Approximately 10% of affected females have seizures or kidney abnormalities. Among those who do have symptoms, they will vary widely from person-to-person.
Triple X syndrome treatment varies and depends on which symptoms are present, and how severe they are.
Unlike the majority of other chromosomal conditions, there is usually no clear visual difference between a female with triple X syndrome and other females. Some females with triple X syndrome may be taller than average. Most individuals with the syndrome have normal sexual development and can conceive children. Infertility is possible in some cases, but it is rare.
Most medical professionals do not regard the condition a disability.
According to Medilexicon's medical dictionary:
Triple X Syndrome is "trisomy of the X chromosome; original observations (made in mental institutions) were seriously biased and the phenotypic changes spurious. Intelligence may be at the lower range of normal, stature is usually tall, there may be speech and behavioral problems. The outstanding feature of the syndrome is the occurrence of twin Barr bodies in a typical cell."
What are the signs and symptoms of triple X syndrome?
A symptom is something the patient senses and describes, while a sign is something other people, such as the doctor notice. For example, drowsiness may be a symptom while dilated pupils may be a sign.
In all female cells, only one X chromosome is active at any time. Consequently, triple X syndrome generally does not cause unusual physical features or medical problems. In other words, in the majority of cases there are no signs or symptoms. If symptoms do occur, they may include:
- If physical features are present they will be very mild:
- Tall stature
- Microcephaly (small head)
- Epicanthal folds - a vertical fold of skin that comes down across the inner angle of the eye.
- Increased width between the eyes
- Tall stature
- Delayed language skill development
- Delayed motor skill development, resulting in poor coordination, awkwardness, and/or clumsiness.
- In very rare cases, infertility
- Some may have menstrual irregularities
- Some may experience an early onset of menstruation
If signs and symptoms are present, they will vary a lot between individuals.
What are the causes of triple X syndrome?
What are genes, chromosomes and DNA?
Anything that lives has genes. Genes are a set of instructions that decide what the organism is like, how it survives, and how it behaves in its environment. The genes lie in long strands of DNA (deoxyribonucleic acid) called chromosomes. Humans have 23 pairs of chromosomes - or a total of 46. A donkey has 31 pairs of chromosomes, a hedgehog has 44, and a fruit fly has just 4. An enormous number of genes lie in each chromosome strand. Scientists say that a chromosome is a single piece of DNA which has many genes, regulatory elements and other nucleotide sequences (sequences of the letters ACGT).
A chromosome consists of DNA and has proteins attached to it. These chromosomes are located in your body's cells, which then contain this important genetic information held in the long strands of DNA.
Your genes decide virtually everything about you. Your genes decide whether you are tall or not, the color of your hair, the color of your skin, whether you are more likely to develop certain diseases, whether you are good at sports, how you respond to environmental triggers, what you look like inside and out, and what sex you are.
Chromosomes that determine our sex
One of the 23 chromosome pairs that humans have determine our sex. We receive:
- One sex chromosome from our mother, whose chromosome pair is XX. Females have an XX pair. A mother can only pass on an X chromosome.
- One sex chromosome from our father, whose chromosome pair is XY. Males have an XY pair. A father can pass on either an X or a Y chromosome.
If an offspring receives an X chromosome from the father she will be female - because the mother will pass on an X chromosome, giving the offspring an XX chromosome pair; making her female. If the father passes on a Y chromosome, the offspring will have an XY chromosome pair, making him a male.
Individuals with triple X syndrome have an extra X chromosome, on top of the XX pair - in other words, they are females (XX) with an extra X chromosome (XXX).
Experts say this occurs because either:
- The mother's egg was not formed properly (nondisjunction)
- The father's sperm was not formed properly (nondisjunction)
- Something went wrong during the development of the embryo (mosaic form of triple X syndrome)
Triple X syndrome is not an inherited condition.
The presence or severity of symptoms depends partly on how many body cells have the extra X chromosome. If the syndrome is caused by a badly formed egg or sperm every cell in the body has that extra chromosome. In the mosaic form of triple X syndrome only a number of body cells have the extra chromosome. Most cases of triple X syndrome are caused by a malformed egg or sperm.
Triple X syndrome is sometimes called 47, XXX syndrome because the extra chromosome gives that human 47 chromosomes (instead of the usual 46).
Diagnosing triple X syndrome
Triple X syndrome is diagnosed before the baby is born, through CVS (chorionic villus sampling) or amniocentesis, and a blood test after she is born.
- CVS (chorionic villus sampling) - tissue is taken from the villi (vascular fingers) of part of the placenta (chorion) and examined. It is usually done between the 8th and 10th week of pregnancy, usually to diagnose severe abnormalities afflicting the fetus (unrelated to triple X syndrome).
- Amniocentesis - also known as an amnio. Done during pregnancy in which some amniotic fluid is collected and diagnosed for a genetic or some other condition. The fetus/embryo floats in amniotic fluid.
- Blood test - a chromosome analysis is done if the doctor notices unusual physical features of delays in development.
All three tests can look at the person's Karotype (collection of chromosomes).
There is no routine screening for triple X syndrome. If an embryo/fetus is found to have the syndrome, it is usually after screening for something else.
What are the treatment options for triple X syndrome?
It is not possible to remove the extra X chromosome. Treatment will depend on the needs of the girl. The patient may have been seen by physical, developmental, occupational or speech therapists if developmental or speech problems have occurred. If there are social problems she may have also been seen by a pediatric psychologist.
Treatment for developmental or psychological symptoms will be the same as for any child with such problems. If she has a learning disability she should receive the same counseling and support as anybody else with that type of learning disability.
A supportive environment is crucial, especially for girls with triple X syndrome who may be more susceptible to stress.
A girl with triple X syndrome who receives proper help and support can lead a full and normal life.
What are the possible complications of triple X syndrome?
If the girl has developmental delays, motor skill delays and difficulties, and does not get proper and prompt help and support, she may suffer from undue stress and anxiety which may eventually lead to psychological problems and social isolation.
The right help and support is extremely helpful for a girl with triple X syndrome who has symptoms.
Written by Christian Nordqvist
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