What is Fragile X syndrome?

Fragile X syndrome (or FXS) is a genetic condition that causes intellectual disability and/or behavioral problems. Symptoms may include learning and intellectual disabilities, delays in speech development and behavioral changes. Fragile X syndrome is the most common cause of inherited (a change that can be passed from one generation to the next) intellectual disability and autism spectrum disorders.

How is the test performed?

A small blood sample is collected from the child and is sent to the lab for analysis. The lab will issue a report of findings to the healthcare provider who ordered the test. Your healthcare provider will then discuss these results with you, and together you can decide on the next steps for your child’s health care.

What will I learn from the results of this test?

This test will tell you whether or not your child has a change in the FMR1 gene that causes fragile X syndrome. In some cases, the test may identify a change that does not cause fragile X syndrome, but could lead to other associated health problems that can affect fertility or cause tremors later in life. Because fragile X syndrome is inherited, it is important to inform other family members who may be at risk.

Receiving a genetic diagnosis can help you better understand your child’s condition. It can be easier to understand future health problems and may help predict what to expect as your child gets older. It also may allow you and your healthcare providers to work together to give your child specialized medical care at an earlier age in order to maximize his or her potential.

What causes Fragile X syndrome?

FXS is caused by changes in the fragile X gene (or FMR1) located on the X chromosome. Females have two X chromosomes (XX) and males have an X and a Y chromosome (XY). A girl will receive an X chromosome from each parent, while a boy will receive the X chromosome from his mother and a Y chromosome from his father. Males who inherit a non-working copy of the FMR1 gene (located on the X chromosome) are often more severely affected than females because they have only one X chromosome.

Fragile X is caused by repeats of DNA (the building blocks of our genetic code) in the FMR1 gene. While everyone has these repeats inside the FMR1 gene, it’s an expanded number of repeats that can cause fragile X. Test results fall into four categories based on the number of repeats:

Talk to your healthcare provider to find out if this test is right for your child.