Letters Section Editor: Robert M. Golub,
MD, Senior Editor.
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.
Toft M, Farrer M. Premutation Alleles and Fragile X–Associated Tremor/Ataxia Syndrome. JAMA. 2005;293(3):296-297. doi:10.1001/jama.293.3.296-a