Fragile X Syndrome: The Forgotten Cause of Intellectual Disability

Intellectual and developmental disabilities (IDDs) dramatically impact the quality of a person’s life. While plenty of media attention has been devoted to autism, Fragile X Syndrome (FXS) remains among the most misunderstood cause of intellectual disability. Unlike autism or other intellectual disabilities, reports Healthline, FXS affects less than 0.025 percent of males and 0.0125 percent of females.

The presentation of FXS in males tends to be more severe than in women. Since the prevalence of FXS has left it far behind the research of autism or other developmental disabilities, you need to understand its causes, new treatment methods and problems associated with advancing the knowledge base of this disorder.


Causes of FXS

FXS is a type of genetic disability. FXS is passed one through a genetic alteration in the FMR1 gene. In most people, the DNA segment of this gene is repeated between five and 40 times. In people with FXS, the genetic sequence is repeated more than 200 times. Logically, the repetition should not cause any problems. However, the excess length of the gene results in its silencing the gene’s expression. In other words, the entire FMR1 gene becomes ineffective.

When the FMR1 gene does not become active, a key protein, the fragile X mental retardation protein, explains the National Human Genome Research Institute (NHGRI) is lost. As a result, the person develops the signs and symptoms of FXS and intellectual disability.

Part of the reason the gene’s missing expression results in more severe intellectual disability for males revolves around basic genetic concepts. Males have only one X chromosome, and females have two. If the FMR1 gene is not active on one chromosome in females, its pairing X chromosome may have the correctly functioning gene. Therefore, the gene and its encoding for necessary proteins remains intact.

Females that carry the mutation on both X chromosomes also may exhibit milder cases of intellectual disability, and some may even live with FXS without realizing it.


How is FXS Treated?

Treatment is aimed at helping people with the Developmental Disability to minimize the symptoms of the condition. Those living with FXS may experience problems with social or emotional development and problems communicating, explains MedlinePlus. However, given the appropriate education, therapy services, and medications, all persons with FXS can make progress.

Diagnosing FXS has grown much easier with the rise of genetic testing. A single blood test can diagnose FXS, but a cure remains out of reach. According to, an organization dedicated to advancing treatments and research of FXS, the strategy behind FXS research is evolving, which includes developing better treatment target goals, preclinical studies and launching clinical trials of possible vaccines or protein-like remedies.

Like many other Developmental Disabilities, all research gathered from studies and these trials must rely on behavior analysis and intervention methods to assess the level of improvement achieved with each respective treatment method. In the use of medications, researchers must also review how the potential side effects of the medications may impact future quality of life as well.


Why Do Researchers Continue to Have Problems With Fragile X Syndrome Research?

The biggest problem faced with ongoing research of FXS is availability of those with this intellectual disability. As mentioned previously, the number of people living with full expression of FXS is minimal.

Meanwhile, only 44 percent of women and 9 percent of men living with FXS reach a “high level of independence as adults.” In other words, the overwhelming majority of men with FXS require assistance with basic daily activities as adults. As a result, they may be incapable of getting to or participating in clinical studies or trials.

The presence of FXS is also a factor in the development of autism spectrum disorder (ASD) seizure disorders and problems with the cardiovascular system, reports the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). Although this information was last reviewed in 2013, further research has not been conducted since to generate different risk profiles for other co-occurring intellectual or physical health disabilities with FXS.

Researchers must also determine how the transmission of the faulty FMR1 gene may have occurred.

For example, a father with a mild premutation and a mother with one mutated chromosome may have a higher risk of the missing gene expression. In addition, a mother with a premutation of FMR1, consisting of 70 to 79 repetitions, has approximately a 30 percent chance of passing on a full mutation to a child.

Ultimately, the treatment devised for each case of FXS must consider how many times the FMR1 gene is repeated. If the repetition approaches its the 200-repeat mark, the treatment must become more involved and may require medications and therapy to be effective.


The Big Picture

The risks of being diagnosed with FXS are dramatically increased when both parents have mild forms of intellectual disability due to premutation or mutation of the FMR1 gene. Unfortunately, FXS is often overlooked as a type of intellectual disability, resulting in missed treatment and intervention opportunities.

In parents with known cases of premutation or mutation, blood tests can immediately detect the lack of protein synthesis from an FMR1 deletion. Currently, the NICHD has been conducting a study since 2009 on the use of medications to correct the protein deficiency found in those with FXS. However, the study requires years of research and ongoing review to create a comprehensive set of guidelines for its use.

The key to understanding FXS is no different than ASD and other types of  Developmental Disabilities. Therapists and direct support professionals must watch for the development of cognitive problems in those with a family history of  Developmental Disabilities. Since FXS may not have been diagnosed in close family members in the past, the prevalence of FXS may change in coming years. However, early intervention is important, and by understanding more about it, you can do something to help the people living with FXS.

Jason Vanover

Working in health care since 2005, Jason's body of experience encompasses dozens of care settings, including Senior care, psychiatric facilities, nonprofit health service centers, group homes for those with developmental disabilities and beyond. Jason understands the need to tailor his skills to each setting to encourage the best treatment outcomes and promote an inclusive, healing environment.

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