TOR1A and Dystonia: Second, in the studies restricted to DRD or inherited dystonia caused by a single gene, such as DYT1, manifesting mainly in generalized dystonia, the included patients were limited because of the disease rarity [dystonia classification/number of patients; DRD/n = 8 (4), DRD/n = 2 (5), DYT1/n = 1 (6), DYT11/n = 1 (7)].