Candidate gene studies in focal dystonia

Background: Genetic susceptibility factors for focal idiopathic torsion dystonia (F-ITD) are not established. Mutations in the DYT1 gene can cause focal dystonia, and an association with a polymorphism in the D5 receptor gene (DRD5) has been reported but not confirmed. Objective: To investigate a possible role of DYT1 polymorphisms, a CA repeat in the D5 receptor gene (DRD5), the human leukocyte antigen (HLA)-DRB locus, and four polymorphisms in the homocysteine metabolism in the pathogenesis of F-ITD. Methods: Initially, 100 German patients and 100 matched control subjects were investigated. A second French population with 121 F-ITD patients and matched control subjects was also studied. Results: Two polymorphisms of the β-cystathionine synthase gene were associated with F-ITD in the German population, but this finding was not replicated in a second independent F-ITD patient and control group of French origin. None of the other investigated polymorphisms was associated with F-ITD. The authors failed to confirm a previously reported association with a polymorphism in DRD5. Conclusion: No evidence for an involvement of DYT1, DRD5, HLA-DRB, or polymorphisms in the homocysteine pathway in the pathogenesis of F-ITD was found.