FXS is caused by problems with the FMR1 gene. These problems prevent fragile X mental retardation protein (FMRP) from developing. The protein helps to make connections in the brain. Without the protein, certain connections in the brain cannot be made. This causes developmental problems and prevents children from fully developing some higher cognitive functions.
The main risk factor for FXS is having a parent with an FMR1 mutation. Most people who inherit a minor mutation, which is sometimes called a premutation, do not develop the symptoms and signs of FXS. A few premutated children may show signs that resemble autism. Others, primarily males, may develop a set of neurological symptoms called fragile X tremor ataxia syndrome in later adult life. Females may develop FMR1-related premature ovarian insufficiency.
Children of mothers with FMR1 premutations are at risk of inheriting a fully mutated FMR1 gene severe enough to cause symptomatic FXS. If a woman does not have symptoms and is a carrier of an FMR1 mutation or premutation, each child of hers has a 50% chance of inheriting that gene. Of the children that inherit that gene, boys are much more likely to develop symptoms than girls. The severity of the disorder may vary between different individuals in the same family.
In general, each generation tends to have worse mutations and a higher risk of FXS than the previous one.
The number and severity of symptoms varies widely. Symptoms tend to be less frequent and milder in females. Symptoms can include:
ranging from learning disabilities to intellectual disability
Low muscle tone and delayed motor skills such as sitting and walking
You will be asked about your child's symptoms and medical history. A physical exam will be done. FXS may be suspected if a child has:
Physical, cognitive, or emotional symptoms of FXS
Unexplained developmental delays or intellectual disability
The diagnosis can be confirmed by genetic testing with a DNA blood test.
There is no cure for FXS. Treatment is aimed at controlling symptoms. Treatment may include:
Medications used to treat symptoms of FXS include:
Stimulants and other medications to treat attention deficit/hyperactive behavior
Psychotherapeutic drugs such as fluoxetine to help control:
Anticonvulsants to control seizures
Specific therapies depend on the degree of developmental delays, intellectual disability, or behaviors. These may include:
Specific educational strategies depend on the degree of developmental delays and/or intellectual disability. Educational strategies include setting a stable educational environment for the patient that includes:
School work that only requires a short attention span
Predictable activities and classroom routine
Close communication between parent and school
Emphasis on functional life skills
There are no known ways to prevent FXS once a person is born. If you have FXS or risk factors for FXS, you can talk to a genetic counselor when deciding to have children.
Fragile X syndrome overview. National Institute of Child Health and Human Development website. Available at: http://www.nichd.nih.gov/health/topics/fragilex/Pages/default.aspx. Updated October 29, 2013. Accessed May 6, 2016.
What is fragile X? FRAXA Research Foundation website. Available at: http://www.fraxa.org/fragilex. Accessed June 24, 2013.
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