Genetic study of idiopathic torsion dystonia in Russia

Inheritance of idiopathic torsion dystonia (ITD) was studied in 41 Russian families including 41 probands with generalized, focal; and segmental dystonia and 140 recurred cases. Affected relatives appeared in two or more generations in 31 families analyzed. It was shown that in 76% of segregated cases, ITD was inherited as an autosomal dominant trait with a penetrance of 40% and varying expression. An autosomal recessive type was observed in 24% of the cases. Approximately 10% of the cases of disease could be caused by a new mutation and 14.6% by a nongenetic phenotype similar to genetic forms in its clinical symptoms. ITD with the X-linked recessive type of inheritance did not occur in the families studied The recurrence risk was 20% in autosomal dominant forms. The risk correlated with age the relative's: clinical symptoms developed in 98.4% of patients by the age of 30.