Disease Spotlight: Triple X Syndrome

There are some people who have a chromosome abnormality, a type of genetic condition, who can live their whole life and never know they have the condition. Often a person will only find out if they by chance are tested by a doctor or they have a desire to have children and discover they cannot get pregnant. Sometimes a woman can find out she has a chromosome abnormality if she does a genetic screen during pregnancy that analyzes the maternal and fetal DNA. As genetic technology advances, more of these “mild” chromosome abnormalities that would have never been identified before are being found early on in pregnancy. One such condition is called Triple X syndrome, or Trisomy X.

To review, our bodies are made up of billions of cells. Inside each one of those cells are our genetic instructions, which are bundled up into packages called chromosomes. We have 23 pairs of chromosomes, one set that comes from our mother and one set that comes from our father. A female typically has two X chromosomes, and a male has one X and one Y. If a female has triple x syndrome, instead of having the typical two X chromosomes, she has three X chromosomes. This can occur when an early embryo is copying its genetic instructions and dividing its cells to grow, and the genetic instructions accidentally get stuck together. 

Triple X syndrome typically goes undiagnosed as we previously discussed unless found during pregnancy or by mistake. Females with Triple X syndrome can be taller than average but typically have no other physical features of the condition. Triple X syndrome can be associated with an increased risk of learning disabilities and delayed development of speech and language skills. There is also a possibility, although not as common, of delayed development of motor skills, weak muscle tone, and behavioral and emotional difficulties. In 10 percent of females with triple X syndrome, they can experience kidney abnormalities and seizures as well. 

This chromosome abnormality occurs in about 1 in 1,000 newborn girls. Approximately 5 to 10 girls are born with triple x syndrome every day in the United States. The majority of cases of triple x syndrome are not inherited and simply occur sporadically.

There is currently a genetic screen that can be performed during pregnancy to evaluate the pregnancy for common chromosome abnormalities. This screen is called noninvasive prenatal testing / screening, also known as cell free fetal DNA screening. This screen analyzes fetal DNA that circulates in maternal blood. By drawing the mother’s blood, the screen can place a pregnancy at high risk or low risk for Down syndrome, Trisomy 13, Trisomy 18, and Turner syndrome. In addition, the screen can determine the gender of the baby due to analyzing the sex chromosomes. While not explicitly stated, by analyzing the sex chromosomes most genetic testing labs will also report if there are any abnormalities seen, such as triple x syndrome. Confirmation of triple x syndrome in pregnancy can be completed by diagnostic testing.

If a person suspects they have triple x syndrome and wants to know prior to having children or for their own knowledge, a chromosome analysis can be performed by blood draw. If a woman is found to have triple x syndrome, there is an increased risk of her pregnancy to also have triple x syndrome. 

If you are interested in pursuing testing for yourself or your pregnancy, or have a family history of chromosome abnormalities, please contact AT-GC to schedule an appointment with a genetic counselor. 

Resources:

https://medlineplus.gov/genetics/condition/triple-x-syndrome/#inheritance

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