Genetic analysis of FMR1 repeat expansion in essential tremor.

We performed an association analysis of Fragile X mental retardation 1 (FMR1) CGG repeats in 321 essential tremor (ET) cases and 296 controls at Columbia University. In addition to analyzing the allele distribution (10-49 CGG repeats) in the entire sample, we also performed a screen for ET cases with the FMR1 premutation allele (55-200 CGG repeats), and evaluated an association between ET and FMR1 alleles that included gray zone alleles (41-54 CGG repeats). CGG premutation alleles and gray zone alleles were rare in ET cases, and we found no evidence for association of premutation or gray zone alleles with ET. These data suggest that FMR1 CGG repeats are not a genetic risk factor for ET.