Triple X syndrome: Symptoms, chromosomes, diagnosis, and treatment

Triple X is a chromosomal abnormality that affects approximately 1 in 1,000 women and girls. Normally, a 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 National Institutes of Health (NIH) 5-10 girls with triple X syndrome are born in the United States each day.

The syndrome generally results from a mistake in the formation of the father’s sperm cell or the mother’s egg. Sometimes, triple X syndrome occurs when something goes wrong in the development of the embryo.

Fast facts on triple X syndrome:

Triple X syndrome is also known as Trisomy X, 47 XXX, Triplo-X, and XXX syndrome.

It is not an inherited condition; in other words, it is not passed on from parent to child.

It is caused by a random genetic error.


Cross-section graphic of an X chromosome
Triple X syndrome occurs in girls when they have three X chromosomes, instead of two.

In all-female cells, only one X chromosome is active at any time. Because of this, triple X syndrome does not usually cause unusual physical features or medical problems.

Some people have no symptoms at all, but some may have mild or severe symptoms. Symptoms vary from one person to another.

If signs or symptoms do occur, they may include:

Slightly taller stature.

Slightly smaller head.

A vertical fold of skin that comes down across the inner angle of the eye.

Abnormally curved pinky fingers.

Developmental issues such as delayed language skills and delayed motor skills, which can result in poor coordination, awkwardness, and clumsiness.

Behavioral and emotional difficulties.

More rare symptoms include:


kidney problems

abnormalities of the ovaries

late or early puberty

flat feet

abnormal breast bone

abdominal pains


heart abnormalities

susceptibility to urinary tract infections

Most girls and women with the syndrome have normal sexual development and can conceive children. Very rarely, reproductive issues can arise, including menstrual irregularities, early menstruation, and, occasionally, infertility.

A person with triple X syndrome does not normally look different from people without the syndrome.
Many medical professionals do not regard the condition as a disability.

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Everything 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. Genes occur in long strands of DNA called chromosomes. Chromosomes are found in virtually all the cells of the body. Genes decide whether a person will be male or female, tall or short, and what color their hair and skin will be. They also affect the risk of developing certain diseases, and how an individual responds to environmental triggers.

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.

One of these 23 chromosome pairs in a human determines whether the person will be a man or a woman. Each person receives one sex chromosome from their mother and one from their father.

Females have an XX pair, so a mother can only pass on an X chromosome. Males have an XY pair, so a father can pass on either an X or a Y chromosome.

If a fetus receives an X chromosome from the father, she will be female, because the mother will pass on an X chromosome. This will give her an XX chromosome pair.

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, as well as the XX pair. In other words, they are females (XX) with an extra X chromosome (XXX).

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