Primary torsion dystonia: the search for genes is not over

A GAG deletion in the DYT1 gene accounts for most early, Limb onset primary torsion dystonia (PTD). The genetic bases for the more common adult onset and focal PTD are less well delineated. Genetic loci for an "intermediate d ystonia" phenotype and for torticollis, named DYT6 and DYT7 respectively, h ave recently been mapped in single families. To evaluate the contribution o f these genetic loci to other families with familial "non-DYT1" dystonia fi ve large families with dystonia were studied using genetic markers spanning the DYT6 and DYT7 regions. There was no evidence of linkage to either locu s in any family. These findings illustrate the genetic heterogeneity of the dystonias and indicate the existence of one or more as yet unmapped genes for dystonia, Large collaborative efforts will be required to identify thes e, and additional genes, causing PTD.