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Genetic and Rare Diseases Information Center (GARD)

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Fragile XE syndrome

Other Names for this Disease
  • Fragile site, folic acid type
  • FRAXE syndrome
  • X-linked mental retardation associated with fragile site FRAXE
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I would like some information on Fragile XE (FRAXE) syndrome.

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What is Fragile XE syndrome (FRAXE) syndrome?

Fragile XE syndrome is a genetic condition associated with mild to borderline intellectual disabilities (IQ = 50-85) with physical features differing from person to person. The characteristic features are learning difficulties, often a consequence of communication problems (speech delay, poor writing skills), and overactivity. Fragile XE syndrome is caused by a specific type of change (mutation) called a trinucleotide repeat expansion that occurs on chromosome X. The repeating trinucleotide in Fragile XE syndrome is CCG. When the number of CCG repeats is over 200, people typically have the signs and symptoms seen in Fragile XE syndrome.[1]

Last updated: 3/15/2010

What causes Fragile XE syndrome?

Fragile XE syndrome is caused by expansion of a CGG repeat on chromosome X near Xq28 (see diagram below). The CGG repeat is normally between 3 to 39 CGG repeat units, with most people having 16-18 CGG repeat units. Once the repeat unit is greater than 200, the FRAXE gene does not work, resulting in the characteristic features of Fragile XE syndrome.[2] 

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Last updated: 9/26/2011

How is Fragile XE syndrome diagnosed? lists the names of laboratories currently conducting genetic testing on a clinical and research basis for Fragile XE syndrome. (To learn about the differences between clinical and research genetic testing, click here.) Click on the links below to obtain the names and contact information of the laboratories. Many laboratories do not accept direct contact from patients and their families; therefore, you may need to work with a health care provider to learn more.

Clinical Testing
Research Testing
Last updated: 6/15/2009

  • Gecz J. The FMR2 gene, FRAXE and non-specific X-linked mental retardation: clinical and molecular aspects. Ann. Hum. Genet. 2000;
  • Rimoin DL, Connor JM, Pyeritz RE, Korf BR. Emery and Rimoin's Principles and Practice of Medical Genetics, 5th ed. Philadelphia: Churchill Livingstone Elsevier; 2007;