[PDF] [PDF] Fragile X Testing - My Doctor Online

[PDF] FRAGILE X SYNDROME (FXS)

The FMR1 gene is on the X chromosome Males mutation, their other, normal X often compensates the full mutation that causes fragile X syndrome

[PDF] Fragile X syndrome: - JPEMS

The Fragile-X-Syndrome (FXS) is a genetic syndrome, which causes inherited The mutated gene responsible for Fragile X syndrome is the FMR1 (for Fragile 

[PDF] Handbook-FXD 3rd Edition - The National Fragile X Foundation

ataxia syndrome (FXtas), an adult onset neurological disorder that affects more males than females the changes in the Fragile X gene that cause FXd can

The fragile X syndrome - Journal of Medical Genetics

exon ofthe FMR1 gene (the full mutation) Keywords: fragile X syndrome; FMR1 gene; mental retardation mutation causes longer and shorter expan- sions 

[PDF] FRAGILE X DNA TESTING: A GUIDE FOR PHYSICIANS AND

Although fragile X syndrome is the most common cause of inherited intellectual the gene Males with a full mutation are affected with fragile X syndrome

The Fragile X Syndrome - Nature

The fragile X syndrome of mental retardation is one of the most common genetic diseases The mutation causing this dis- ease was the first of a new class of 

[PDF] Fragile X Syndrome - University of Northern Colorado

Nearly all cases of Fragile X syndrome are caused by a mutation in which a DNA segment, known as the CGG triplet repeat, is expanded within the FMR1 gene

[PDF] Fragile X Testing - My Doctor Online

Fragile X syndrome is caused by a genetic change (mutation) in the Fragile X Mental Retardation (FMR1) gene The FMR1 gene makes a protein that is found in 

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TPMG Regional Genetics Laboratory

Fragile X Testing

What is fragile X syndrome?

Fragile X syndrome is an inherited condition that

caus es intellectual disability, behavior challenges, and small differences in the way a person looks.

The level of intellectual

disab ility can range from mild to severe . Common behavior problems include hyperactivity, attention deficit disorder, and autistic behaviors. Females with fragile X syndrome usually have milder symptoms than males. Fragile X syndrome is found in people from all parts of the world. It affects about 1 in every 4000 males and 1 in every

6000 females.

What causes fragile X syndrome?

Fragile X syndrome is caused by a genetic change

(mutation) in the Fragile X Mental Retardation (FMR1) gene. The FMR1 gene makes a protein that is found in the brain and other parts of the body. Almost all cases of fragile X are due to an expansion of the FMR1 gene. In one part of the gene three letters of the DNA code are repeated many times (CGG-CGG-CGG...). This is called a triplet repeat or a trinucleotide repeat. In most people there are fewer than 45 CGG repeats.

When there are more than 200 CGG repeats, the

gene gets turned off, causing fragile X syndrome. This is called a fragile X full mutation. Males with a full mutation will have fragile X syndrome, and about half of the females with a full mutation will have symptoms of fragile X syndrome.

What is a fragile X premutation?

A person with between 55 and 200

CGG repeats

carries a genetic change called a fragile X premutation. Both males and females can have a fragile X premutation. A person with a premutation does not have fragile X syndrome, but could pass the FMR1 gene to their children with more CGG repeats.

Are there any medical problems for a person

with a premutation? Most people with a premutation do not have medical problems. However, some people with a fragile X premutation develop tremors (shaky hands), balance problems, and behavior changes as they age. This is called fragile X-associated tremor/ataxia syndrome (FXTAS). It is more common for a man with a premutation to develop FXTAS. Some women with a fragile X premutation may start menopause earlier than expected. This is called fragile X- associated primary ovarian insufficiency (FXPOI).

Why should I consider fragile X

testing? Fragile X testing lets you know if your child could be born with fragile X syndrome. Testing can also let you know if you are at risk for FXTAS or FXPOI. A genetic counselor can help by reviewing your family history to find out whether fragile X testing may be indicated for you or someone in your family.

Fragile X testing may be offered if you have:

Delayed development, intellectualdisabilities, or autism Significant learning disabilities, especiallywhen there are behavior problems or physical differences

Someone in the family with fragile X

syndrome A family history of intellectual disability thatsuggests fragile X syndrome

Early menopause (before 40)

Development of tremors, balance problems,and behavior changes without a knowncause, especially if you are a male over 50

TPMG Regional Genetics Laboratory

Fragile X Testing

How is testing done?

Fragile X testing is

usually done on a blood sample . Testing can also be done during pregnancy to check a fetus for fragile X. In the laboratory, the FMR1 gene is tested to see if a full mutation or a premutation is present.

How accurate is testing?

Fragile X testing is highly accurate. More than

99% of mutations in the fragile X gene will be

found by standard testing.

What are the limitations of testing?

Fragile X

testing does not test for all genetic causes of intellectual disability. If testing is being done because an individual or a family member has intellectual disability, more testing may be needed to look for other genetic causes of intellectual disability. How l ong does i t t ake t o get r esults? ragile X t est are usually ready in about t wo weeks. Fragile X can be passed from a parent to a child, but fragile X inheritance is complex. The FMR1 gene is located on the X-chromosome and is called an X-linked condition. Inheritance is different for females and males. Females: Two X-chromosomes Two copies of the FMR1 gene Males: One X-chromosome One copy of the FMR1 gene

PLUS One Y-chromosome with no FMR1 gene

Female Carriers:

A woman who carries either a premutation or a full mutation can pass the mutation to her sons and her daughters. There is a 50% (1 in 2) chance that the mutation will be passed on. The number of CGG repeats can get bigger when the FMR1 gene is passed from a mother to her child. This means that a child born to a woman with a premutation could have fragile

X syndrome.

Male Carriers:

A man with a premutation will pass the premutation to all of his daughters, but none of his sons (he passes the Y chromosome to his sons). The premutation rarely changes size when it is passed from a father to his daughters.

Resources:

National Fragile X Foundation

- https://fragilex.org/ This information is not intended to diagnose health problems or to take the place of medical

advice or care you receive from your physician or other health care professional. © 2011, The Permanente Medical Group, Inc. All rights reserved. Regional Genetics Department. Rev RL 8.1

Genetics. kp.org

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