Assessing the role of DRD5 and DYT1 in two different case-control series with primary blepharospasm

Primary blepharospasm is a common adult-onset focal dystonia. Polymorphisms of the genes encoding TorsinA (DYT1) and the D5 dopamine receptor (DRD5) have previously been associated with lifetime risk for focal dystonia. We describe here experiments testing common variability within these two genes in two independent cohorts of Italian and North American patients with primary blepharospasm. We have failed to identify a consistent association with disease in the two patient groups examined here; however, analysis of the Italian group reveals an association with the same risk genotype in DYT1 as previously described in an Icelandic population. We have also found global significant DYT1 haplotype differences between patients and controls in the Italian series. These data suggest that further examination is warranted of the role genetic variability at this locus plays in the risk for primary dystonia.