Inherited dystonia designated by DYT locus symbols can be separated into three broad phenotypic categories: primary torsion dystonia (PTD), where dystonia is the only clinical sign (except for tremor) (DYT1, 2, 4, 6, 7, 13, 17, and 21); dystonia plus loci, where other phenotypes in addition to dystonia, including parkinsonism or myoclonus, are present (DYT3, 5/14, 11, 12, 15, and 16); and paroxysmal forms of dystonia/dyskinesia (DYT8, 9, 10, 18, 19, and 20).
Our data suggest that the DYT1 mutation is not associated with significant damage to the nigrostriatal DA system, in keeping with the absence of parkinsonism and levodopa response in this disorder.