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How many people are affected by Fragile X syndrome?

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About 1 in 4,000 males and 1 in 8,000 females have Fragile X syndrome.1

How many people have the Fragile X premutation?

Although Fragile X syndrome is relatively rare, premutations in the FMR1 gene are relatively common: A recent study of 6,747 people found that 1 in 151 women and 1 in 468 men had the premutation.2 People with the premutation might not have any symptoms of Fragile X. However, the premutation can sometimes expand in the next generation, which can cause Fragile X syndrome.


  1. Hagerman, P. J. (2008). The fragile X prevalence paradox. Journal of Medical Genetics, 45, 498−499. [top]
  2. Seltzer, M. M., Baker, M. W., Hong, J., Maenner, M., Greenberg, J., & Mandel, D. (2012). Prevalence of CGG expansions of the FMR1 gene in a US population-based sample. American Journal of Medical Genetics. Part B, Neuropsychiatric Genetics, 159B(5), 589–597. [top]

Last Updated Date: 12/19/2013
Last Reviewed Date: 10/29/2013