INTERFAMILIAL POLYMORPHISM OF TYPE 1 DYSTONIA

Background: The most frequent mutation of the gene TOR1A (DYT1) (9q34), that causes type 1 dystonia (DOPA-unresponsive torsion dystonia) is the deletion c.907-909delGAG in the 5th exon of the gene (303delGlu). This mutation has not been found in the Russian population of patients with cervical dystonia.

Aim: To elucidate the existence and clinical characteristics of interfamilial polymorphisms in type 1 dystonia patients in the Moscow Region.

Materials and methods: Twenty one patients with dystonia underwent molecular genetic tests with DNA sequencing aimed at identification of the DYT1 gene mutation.

Results: Sixteen of 21 patients had only cervical dystonia without the DYT1 gene mutation. Among 5 patients with torsion dystonia, 2 cases demonstrated the most frequent mutation of the DYT1 gene, i.e., the deletion of three nucleotides (del1302/303, orс.907_909delGAG). There were specific characteristics in clinical manifestation and onset of the disease in the patients with the mutation. In a 30-year old patient the disease manifested at the age of 14 with torsion dystonia. In a 50-year old patient the disease manifested at the age of 46 from trunk dystonia, which at the age of 48 was followed by cervical dystonia (left-side torticollis), where two courses of botulin treatment (type A botulinic toxin complexed with hemagglutinin, 300 U) were minimally effective.

Conclusion: No mutation in the DYT1 gene was found in the population of patients with cervical dystonia in the Moscow Region, which agrees with the literature data. In those with torsion dystonia, the DYT1 gene mutation was found in 2 of 5 (40%) cases. Interfamilial polymorphism of the disease was identified.