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To the Editor: The study by Dr Deng and colleagues¹ stated that premutation carriers of the fragile X mental retardation 1 (FMR1) gene are at high risk of developing fragile X–associated tremor/ataxia syndrome (FXTAS) and spinocerebellar ataxia. Their reference² and a recent study by Van Esch et al³ found FMR1 premutation carriers in male patients referred for testing of spinocerebellar ataxia genes. However, most of the premutation carriers identified in these 2 studies showed cerebellar white matter abnormalities on imaging, and they fulfilled the diagnostic criteria for FXTAS, which include intention tremor, gait ataxia, parkinsonism, cognitive symptoms, and pathology evident on magnetic resonance imaging.⁴ Such patients should therefore not receive a diagnosis of spinocerebellar ataxia.

Mathias Toft, MD
toft.mathias@mayo.edu

Matthew Farrer, PhD
Udall Center of Excellence in Parkinson Disease Research
Department of Neuroscience
Mayo Clinic Jacksonville
Jacksonville, Fla

1. Deng H, Le W, Jankovic J. Premutation alleles associated with Parkinson disease and essential tremor. JAMA. 2004;292:1685-1686. FREE FULL TEXT 2. Macpherson J, Waghorn A, Hammans S, Jacobs P. Observation of an excess of fragile-X premutations in a population of males referred with spinocerebellar ataxia. Hum Genet. 2003;112:619-620. ISI | PUBMED 3. Van Esch H, Dom R, Bex D, et al. Screening for FMR-1 premutations in 122 older Flemish males presenting with ataxia. Eur J Hum Genet . Published October 13, 2004. Available at: http://www.nature.com/ejhg/journal/vaop/ncurrent/pdf/5201312a.pdf. Acessibility verified December 13, 2004. 4. Jacquemont S, Hagerman RJ, Leehey M, et al. Fragile X premutation tremor/ataxia syndrome: molecular, clinical, and neuroimaging correlates. Am J Hum Genet. 2003;72:869-878. FULL TEXT | ISI | PUBMED

Letters Section Editor: Robert M. Golub, MD, Senior Editor.

JAMA. 2005;293:296.

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