Fragile X Syndrome

Fragile X syndrome facts*

*Fragile X syndrome facts medical author:

  • Fragile X syndrome (also called Fragile X) is the most common inherited form of mental problems (mental retardation).
  • Fragile X syndrome is caused by changes in a single X chromosome (FMR1).
  • FMR1 does not produce enough protein (FMRP) that works cell communication.
  • Normal X genes that control FMR1 levels have promoter regions consisting of about 6 to 40 CGG; Fragile X genes have about 55 to 200 (termed premutation) or more than about 200 regions (termed full mutation).
  • About 100 trillion cells make up a human body and each should have 46 chromosomes, but males have only one X chromosome; so, if it contains a FMR1 chromosome, the effect of the lack of FMRP is more significant than in females.
  • Approximately one in 3,600 to 4,000 males is affected by the full mutation of the FMR1 gene, and about one in 468 males has the premutation form of the FMR1 gene; about one in 151 females in the general population has the premutation while about one in 4,000 to 6,000 females is affected by the full mutation (these are estimates only).
  • The Fragile X gene is only carried on an X chromosome; both males and females may transmit a Fragile X (FMR1) gene on their X chromosome.
  • The signs and symptoms of Fragile X syndrome have five general categories where individuals often show altered or arrested development: intelligence and learning (low IQs); physical (long face or jaw, short stature, enlarged testicles); social and emotional (anxiety); speech and language (stuttering and disorganized speech); and sensory (sensitive to certain stimuli like sounds, balance problems). Each individual may exhibit variations in these categories.
  • Currently, there is no cure for Fragile X syndrome nor are there any definitive treatments other than helping the individual develop to their maximal potential through education; therapies such as speech, language, behavioral, and physical; and other therapies.
  • Medication therapy may only help certain individuals with certain severe problems and should be prescribed only by the patients' doctors; there is no medication that can cure Fragile X syndrome.
  • Adults with Fragile X syndrome may benefit from a team approach to help the patient adjust to independent living, if possible.
  • If a family member has been diagnosed with Fragile X syndrome, other family members may want to be tested to determine if they carry a Fragile X chromosome; there are several accurate DNA tests available for gene testing and for quantizing the amount of FMRP produced. Prenatal tests are also available.
  • Research is ongoing; gene therapy, gene activation, and FMRP replacement therapy are several areas that may lead to treatments, or possible cure or prevention, in the future.
  • Several national organizations may provide additional information on Fragile X syndrome (for example, American Association on Mental Retardation and the National Institute of Child Health and Human Development).
Medically Reviewed by a Doctor on 4/4/2014

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Fragile X Syndrome - Experience Question: Please describe your experience with fragile x syndrome.
Fragile X Syndrome - Symptoms Question: What symptoms do you or your loved one experience from fragile X syndrome? How do you cope?
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A diagnosis of fragile-X associated tremor/ataxia syndrome did not come easy for Marcia and Henry.

Two Newlyweds Fight Fragile-X Associated Tremor/Ataxia Syndrome (FXTAS)

One caregiver's story

Reviewed by Melissa Conrad Stöppler, MD

My name is Marcia*, but sometimes I call myself the "bride of FXTAS." FXTAS stands for Fragile-X Associated Tremor/Ataxia Syndrome, the degenerative neurological disorder that attacked my 64-year-old husband Henry* a month after we were married in 1999. The first noticeable symptom was that Henry fell down while playing golf—medics were called and could find nothing apparently wrong with Henry. It took over five years of worsening symptoms—including more frequent falls, difficulty walking, cognitive decline and incontinence—examinations by five neurologists and many diagnostic tests before Henry was diagnosed with FXTAS.

For the seven-plus years of our marriage, I have been Henry's medical advocate, as his mind was failing, and his primary caregiver, since he gradually lost the ability to walk or do activities of daily living on his own. The journey to a diagnosis began when Doctor #1 suggested Henry might have Parkinson's because of his stiffness and falling; she did several tests and then just never returned our calls because she clearly didn't know what to say. Doctor #2 gave Henry two Parkinson'sdrugs, but they had no effect; his next guess was that Henry had some small strokes(per his MRIs) and he sent Henry to Doctor #3 for another opinion. Doc #3 said it was not strokes, but determined that Henry had a small amount of peripheral neuropathyin his legs; he just called the problems "old age" and prescribed physical therapy. Subsequently, after Henry had a bad fall resulting in a broken arm, we tried Doc #4, who couldn't diagnose Henry, so he called the condition multisystem atrophy, and prescribed more physical therapy. The therapist gave up on Henry since she couldn't figure out how to help him. She suggested we just get Henry a scooter to get around.

*Names have been changed to maintain privacy.


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