The Importance of Testing for Fragile X Syndrome

Leah W. Burke, MD, FACMG, FAAP

July 15, 2020

Brian was a healthy baby and always seemed happy. He seemed to do things on his own schedule, but when he had very little communication at 16 months and his muscle tone seemed lower than expected, he was given a developmental evaluation and found to be delayed in several areas.

His parents came into my clinic when Brian’s developmental pediatrician referred him for a genetic evaluation. Part of the genetic work-up we did was a Fragile X DNA test. When those results came back positive, his parents were surprised to hear that Brian had Fragile X syndrome.  They thought that he was just a little slow with his language and that he might be autistic. They didn’t think he looked different enough to have a syndrome.

Not all children with Fragile X have distinctive features, which is why it’s important to test. Fragile X is a genetic condition that occurs because of a change in a gene on the X chromosome. Because boys have only one X chromosome, changes in this gene usually affect boys rather than girls. Fragile X syndrome – the most familiar of the Fragile X-associated disorders – is one of the most common genetic causes of intellectual disability.

As pediatricians, we know about the importance of developmental evaluations. We know that when children receive services at an early age, the benefit is greater. And while primary care pediatricians have historically been at the forefront of initiating therapies for children with global developmental delay or intellectual disability, genetic evaluation and testing is often overlooked.

“There is a high value in getting a genetic test for any child who has unexplained global developmental delay, intellectual disability, or autism spectrum disorder.”

In fact, there is a high value in getting a genetic test for any child who has unexplained global developmental delay, intellectual disability, or autism spectrum disorder. Primary care pediatricians routinely collect family health histories and, according to research from the AAP Periodic Surveys of Fellows, may identify at least one patient as being at risk for a genetic-related disorder per year. Fewer pediatricians, however, order genetic tests themselves. Often this is due to barriers such as cost or lengthy insurance approvals.

Now, with greater integration of genomics into primary care and the availability of genetic testing, diagnosis is much more in reach.  And it can offer important health benefits for the entire family.

Establishing a diagnosis helps the family in health care intervention, future health care planning, future transition of care issues, and family reproductive decision-making. As such, the primary care pediatrician’s role is vital in identifying children with global developmental delay or intellectual disability and facilitating genetic testing early. Fragile X syndrome can only be diagnosed with a special DNA test.

After Brian was diagnosed, his mother asked about having herself tested. She was found to have what is known as a premutation in the Fragile X gene on one of her X chromosomes. Brian was enrolled in early intervention services. When he recently came in for his 2-year-old visit, it was obvious that his mother seemed much more relaxed about how he was doing and she was more hopeful for the future.

Families can be wary of genetic testing especially when they may not understand the benefits or have the time to navigate the insurance approval process that might be involved. We can help reassure them by providing them with as much factual information and resources as possible.

*The views expressed in this article are those of the author, and not necessarily those of the American Academy of Pediatrics.

About the Author

Leah W. Burke, MD, FACMG, FAAP

Leah W. Burke, MD, FACMG, FAAP, is the chairperson of the Executive Committee of the American Academy of Pediatrics Council on Genetics. She is a professor of pediatrics and medicine at The Robert Larner, M.D. College of Medicine at The University of Vermont. She is also a medical geneticist and serves as the director of the University of Vermont Medical Center Clinical Genetics Program.