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Fragile X–associated tremor ataxia syndrome in FMR1 gray zone allele carriers§


  • Funding agencies: This work was funded by the National Institute of Neurological Disorders and Stroke (NINDS) of the National Institutes of Health (NIH) (NS052487 to D.H.), and a Parkinson Research Center grant from the Parkinson's Disease Foundation.

  • Relevant conflicts of interest/financial disclosures: Nothing to report.

  • §

    Full financial disclosures and author roles may be found in the online version of this article.



Carriers of fragile X mental retardation 1 (FMR1) repeat expansions in the premutation range (55–200 CGG repeats) often develop a syndrome of kinetic tremor, cerebellar ataxia, and parkinsonism; designated the fragile X–associated tremor ataxia syndrome (FXTAS). Neurological signs have not been reported in carriers of gray zone (45–54 CGG repeats) expansions.


We describe 3 patients with FMR1 gray zone alleles who meet diagnostic criteria for FXTAS.


Our cases suggest that the definition of the FXTAS may need to be broadened to include individuals with FMR1 repeat expansions in the gray zone. These neurological signs may be due to elevated levels of expanded CGG repeat FMR1 mRNA in the gray zone carriers, similar to the changes seen in premutation carriers with FXTAS. © 2011 Movement Disorder Society