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Fragile X Syndrome

Page history last edited by PBworks 15 years, 11 months ago

by Susan Contess and Christian New

 

 

What is Fragile X Syndrome?

"Fragile X syndrome is the most common inherited cause of mental impairment. The syndrome occurs in approximately 1 in 3600 males and 1 in 4000 to 6000 females" (fragilex.org).  It is a sex-linked disorder caused by a mutation of the FMR-1 gene on the X chromosome.  A lack of the protein created by this gene, FMRP, affects early brain development and can cause mental retardation or learning disabilities, as well as other symptoms.  (Quercia, 430-434)

 

 

What causes Fragile X Syndrome?

FX Syndrome is caused by a mutation of the FMR-1 gene located on the X chromosome.  In almost every affected individual, this mutation is a repeating CGG nucleotide sequence in the gene.  In normal humans, there are between 6 and 54 repeats of the CGG sequence.  People with a premutation have 54 to 230 repeats of the sequence.  Individuals with the Fragile X premutation might show very mild effects of FX Syndrome and are likely to pass it on to their children in either the premutation form or as fully-fledged Fragile X Syndrome.  In individuals with FX Syndrome, there are 230 or more repeats of the CGG nulceotide sequence.  This disables the FMR-1 gene, causing an absence of the FMRP protein and leading to mental retardation and other effects of FX Syndrome.  Currently, researchers do not know the purpose of the FMRP, but suspect that it is involved in early brain development.  (Quercia, 430-434)

 

 

 

 

How is Fragile X Syndrome an inherited disease?

Males who have FX Syndrome (and therefore the fully mutated FMR-1 gene) will pass on their affected X chromosome to all of their daughters.  Affected males will not pass on the disease in any form to their sons (as males only inherit the Y chromosome from their father).  Females with one Fragile X chromosome have a 50% chance of passing on the affected X chromosome to any of their children.  Any male that inherits an affected X chromosome will have FX Syndrome.  However, females who inherit an affected X chromosome may or may not have FX Syndrome.  This is because females have two X chromosomes, and in some cases, the normal chromosome can produce enough FMRP for the brain to develop normally.  Males who have the premutation will pass on the premutation to their daughters, but not to their sons.  Females who have the premutation have a 50% chance of passing it on to any of their children.  However, when a woman passes on the premutation, it is unstable and likely to expand, meaning that more CGG repeats will be added.  Depending on how much it expands, some of her children could have FX Syndrome.  Because the premutation expands into the complete mutation, some families may never have had anyone show signs of FX Syndrome, and then generations later, have a child with FX Syndrome.

 

 

In this pedigree, the female carriers may or may not display Fragile X Syndrome symptoms.

 

The effects of Fragile X Syndrome are worse in males than in females.

 

 

 

 

What are the symptoms of Fragile X Syndrome (in males)?

  • The most prominent effect of FX Syndrome is mental retardation, which is found in nearly all affected individuals (male and female) in varying degrees.

  • Other Behavioral Characteristics

    • hand flapping

    • hand biting

    • poor eye contact

    • speech problems (such as self-repetition)

    • hyperactivity

    • attention deficit disorder

    • emotional disorders (such as aggressive outbursts)

  •  Physical Characteristics

    • ear and sinus infections*

    • large ears

    • velvet-like skin

    • hyperextensible finger joints* (double-jointedness)

    • high arched palate* (in mouth)

    • flat feet*

    • pectus excavatum* ("sunken-in" chest)

    • mitral valve prolapse* (valvular heart disease)

    • macroorchdism (large testicles)

    • cutis verticis gyrata* (furrowing of the scalp)

    • long and narrow face with prominent jaw

*asterisk indicates that these characteristics are associated with connective tissue problems as a result of the Fragile X mutation.

 Some of the physical characteristics found commonly in males with FX Syndrome may also be found in females with the disease, but they are not as common.  (Nelson, 91-93)

 

 

 

 

What are the treatment options for individuals with Fragile X Syndrome?

Currently, there are no known cures for FX Syndrome.  However, it is recommended that children with this disease work with psychologists and special education teachers.  It is also beneficial for affected children to be integrated into a normal school environment, as they will pick up good behavior there from other students.  (Quercia, 430-434)  For people with FX Syndrome, having a daily routine or schedule is very important and will help them to lead an ordered lifestyle.  People who have attention deficit disorder and/or hyperactivity as a result of FX Syndrome could benefit from taking ADHD medication.  Keeping a person with FX Syndrome entertained using toys and snacks can also help to distract them. (fragilex.ca)

 

 

Where else can I find information about Fragile X Syndrome?

 

The National Fragile X Foundation

PO Box 37

Walnut Creek, CA 94597

USA

1-(800)-688-8765

http://www.fragilex.org/

treatment@fragilex.org

 

The American Association on Intellectual and Developmental Disorders (AAIDD)

444 North Capitol Street, NW, Suite 846

Washington, DC 20001

USA

1-(800)-424-3688

http://www.aaidd.org/

 

The Fragile X Research Foundation

45 Pleasant Street

Newburyport, MA 01950

USA

(978)-462-1866

http://www.fraxa.org/

info@fraxa.org

 

Developmental FX

90 Madison Street, Suite 202

Denver, CO 80206

USA

(303)-333-8360

http://www.developmentalfx.org/

info@developmentalfx.org

 

 

Works Cited

 

I have neither given nor received any unauthorized aid on this project.

Susan Contess

Christian New

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