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Single Gene Disorders and Disability (SGDD)
Single Gene Disorders Home > Fragile X Syndrome
Fragile X Syndrome

Three-generation family including grandfather, mother, and sonWhat is Fragile X syndrome?

Fragile X syndrome (FXS) is the most common known cause of intellectual disability, also known as mental retardation, and developmental disability that can be inherited (passed from one generation to the next). The exact number of people who have FXS is unknown, but it is estimated that about 1 in 4000 males and 1 in 6000 to 8000 females have the disorder. Although FXS occurs in both males and females, females generally have milder symptoms. Signs that a child has FXS include not sitting, walking, or talking as early as other children. This is known as having developmental delays. Often, there are other physical and behavioral signs, but features of FXS vary and signs can be subtle and easy to miss. Children often have a typical facial appearance that gets more noticeable with age. These features include a large head, long face, and prominent ears, chin, and forehead. Children who have FXS might also have learning disabilities, speech and language delays, and behavioral problems such as attention-deficit/hyperactivity disorder (ADHD). Males who have FXS usually have some degree of intellectual disability that can range from mild to severe. Females with FXS can have normal intelligence or some degree of intellectual disability with or without learning disabilities. Autism spectrum disorders (ASDs) also occur more frequently in children with FXS.

 
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What is fragile X syndrome?

arrow What causes fragile X syndrome?
  Flash VideoClick to view a video about what causes fragile x syndrome
         [transcript of video]
arrow How does fragile X syndrome run in families?
arrow What health problems can affect people who have a fragile X premutation?
arrow How is fragile X syndrome diagnosed?
arrow What is CDC doing about fragile X syndrome?
 
 
 Additional information
arrow About genes and mutations      
arrow About X-linked conditions    
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Date: September 1, 2006
Content source: National Center on Birth Defects and Developmental Disabilities

 

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Topic Contents
 arrow Single Gene Disorders Home
arrow Duchenne/Becker Muscular Dystrophy (DBMD)
arrow Fragile X Syndrome (FXS)
  arrow What is FXS
  arrow Causes
  arrow Inheritance
  arrow Premutation Health
    Problems
  arrow Diagnosis
  arrow CDC Priorities
          arrow CDC Projects
arrow About Genes and Mutations
  arrow X-Linked Conditions
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Resources
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Duchenne/Becker Muscular Dystrophy (DBMD)
 
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Fragile X Syndrome (FXS)
 
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Genetics at CDC
 
  arrow Other Genetics Resources
     
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Contact Info

Thank you for visiting the CDC-NCBDDD Web site. Click here to contact the National Center on Birth Defects and Developmental Disabilities

For specific medical advice related to these disorders, please contact your health care provider.  For additional questions about the information on this site, please contact cdcinfo@cdc.gov.


 

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National Center on Birth Defects and Developmental Disabilities

National Center on Birth Defects and Developmental Disabilities
 
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