Get access

Fragile X-associated tremor/ataxia syndrome (FXTAS) in grey zone carriers


  • Dr Hagerman's work has been funded by the NIH. Other funding has been received for clinical trials from Seaside Therapeutics, Roche, Forest, Curemark, and Novartis. Dr. Zhang's work has been funded by the NIH. Other funding has been received for clinical trials from Boehringer-Ingelheim, and Allergan. Dr. Zhang serves as consultant and/or adviser for Allergan, Dysport, Teva Neuroscience, and Merz. Dr. Zhang serves as speaker for Allergan, Novartis, and Teva Neuroscience. Dr. Ying Liu's work has been funded by Teva Neuroscience and Allergan. There are no other conflicts of interest from the authors.

Corresponding author: Randi J. Hagerman MD, MIND Institute, University of California Davis Health System, 2825 50th Street, Sacramento, CA, 95817, USA

Tel.: +1 916 703-0247

Fax: +1 916 703-0240



The grey zone (GZ; 45–54 CGG repeats in the FMR1 gene) is considered a normal allele; however, several studies have found a high frequency of GZ in movement disordered populations. Here, we describe neurological features of fragile X-associated tremor/ataxia syndrome (FXTAS) in two carriers of GZ alleles, although FXTAS has been defined as occurring only in premutation carriers (55–200 CGG repeats). Both patients had family members who had premutation and were diagnosed with FXTAS. The presence of relatively high GZ alleles with elevated fragile X mental retardation 1 mRNA (FMR1-mRNA) combined with a family history of FXTAS that may represent a facilitating genetic background for FXTAS are the factors that led to the presence of FXTAS in these individuals with a GZ allele. Further research into clinical involvement of GZ alleles is recommended and the definition of FXTAS may require revision.