Familial essential tremor and idiopathic torsion dystonia are different genetic entities.

Familial essential tremor (ET) is an autosomal dominant disorder presenting as an isolated postural tremor. Its frequent association with dystonia suggests that the two disorders might be pathogenically related. We report the exclusion of the DYT1 locus on chromosome 9q32-34, responsible for idiopathic torsion dystonia (ITD), in two large ET families. We conclude that ET and ITD are distinct genetic disorders.