Fragile X Syndrome is a genetic disorder that affects approximately 1 in 6,000 US females and 1 in 4,000 US males. Here we take a look at what causes Fragile X Syndrome, the disorder’s symptoms and treatments, as well as the importance of genetic carrier screening to avoid passing Fragile X Syndrome on to future generations.
What is the FMR1 gene?
Scientists have established that Fragile X Syndrome is caused by a genetic mutation in the FMR1 gene. The FMR1 gene is a protein-producing gene located on the X chromosome. A genetic mutation can cause the string of DNA to be longer than that normally found, an abnormality known as a premutation.
If a premutation extends past a certain length, that string of DNA effectively shuts down, failing to produce the protein it usually makes. Scientists call this a full mutation. Essentially, a premutation makes a person a carrier of the disorder. A full mutation means that they will have the condition.
Why does Fragile X Syndrome affect males and females differently?
As we have established, the genetic mutation that causes Fragile X Syndrome affects the X chromosome. X and Y chromosomes are sex chromosomes, effectively deciding the sex of an embryo. Two X chromosomes make a girl and an X and a Y chromosome make a boy.
We each have two copies of virtually all of our genes. The human body is incredibly resilient, and gene mutations are actually quite common. If a genetic anomaly arises, the body usually just reverts to the other healthy gene copy, and the mutation is effectively ignored. That person will be a carrier, but will be unaffected by the condition.
Because males inherit just one X chromosome, if that chromosome carries a genetic mutation they have no healthy copy to fall back on. It is for this reason that while females may be carriers, Fragile X Syndrome is much more common in males, whose symptoms tend to be more severe.
What are Fragile X Syndrome’s main symptoms?
Physical signs of Fragile X Syndrome include: a long face; flat feet; large, prominent ears; hyper- extensible joints, particularly in the fingers; enlarged testes following puberty in males; and low muscle tone.
Fragile X Syndrome affects brain development in early infancy. Symptoms include: intellectual impairment, ranging from mild to severe; hyperactivity and attention deficit, particularly in young children; mood swings; anxiety; hypersensitivity to bright lights or loud noises; classic autistic spectrum behaviors, such as avoiding eye contact and hand flapping; delayed speech; and epilepsy. Approximately 25 percent of people who have Fragile X Syndrome experienced seizures.
How is the syndrome diagnosed?
Scientists developed a genetic test for Fragile X Syndrome in 1992. It is simple and highly accurate.
Testing is recommended for anyone showing signs of developmental delay or displaying symptoms associated with the autistic spectrum. These can be exhibited in children, though symptoms may be subtle at first. Experts believe that many people with milder forms of Fragile X Syndrome remain undiagnosed.
Can Fragile X Syndrome be cured?
There is no known cure for this genetic disorder. However, medical practitioners have developed targeted treatments that can be effective in managing symptoms.
Educational and behavioral therapies can be very beneficial. In many cases, early diagnosis is crucial. Studies show that early intervention, ideally before the age of 3 years, can be particularly helpful. In children of school age, an Individualized Education Plan has been shown to help most children, especially when implemented alongside occupational, speech and physical therapies.
There is currently no drug on the market specifically designed to target the symptoms of Fragile X Syndrome. Clinicians often prescribe mainstream medications to manage symptoms.
The FRAXA Research Foundation has achieved significant breakthroughs in recent years through its research into the condition. FRAXA-funded studies have revealed how this genetic disorder affects neurons, brain cells important to learning and memory. These studies have led scientists closer to understanding the disease, paving the way for future development of a cure.
Why is genetic carrier screening so important?
The genetic mutation that causes Fragile X Syndrome is surprisingly common. An estimated 320,000 men and 1 million women in the United States carry this genetic anomaly.
Women who carry the genetic mutation associated with Fragile X Syndrome have a 50 percent chance of passing it on to their child, regardless of whether her partner carries the variant. If a child inherits the gene mutation, the child may be a carrier or may be born with Fragile X Syndrome. If the mother actually has the disorder, that child has a 50 percent chance of inheriting the disorder.
Males have just one X chromosome to pass on, so if that chromosome features the associated genetic mutation, it will pass to all of their daughters. Because sons inherit their Y chromosome from their fathers, affected fathers cannot pass the genetic mutation associated with Fragile X Syndrome to their male children.
Genetic carrier screening provides medical practitioners with insight into the genetic makeup of prospective parents. Preconception carrier screening is particularly helpful, taking the guesswork out of family planning and, in the vast majority of cases, providing parents-to-be with peace of mind.