Idiopathic torsion dystonia: assignment of a gene to chromosome 18p in a German family with adult onset, autosomal dominant inheritance and purely focal distribution.

Idiopathic torsion dystonia (ITD) is a group of movement disorders which is usually inherited in an autosomal dominant manner with reduced penetrance. Most patients with ITD present with focal dystonia at adult age. However, thus far, this common subform remained unmapped chromosomally. In contrast, a rare early onset, more generalized form of ITD has been mapped to chromosome 9q34. Our linkage study in a large pedigree with seven definitely affected, six possibly affected and 16 phenotypically unaffected family members assigns an ITD gene for the common focal form with a maximal lod score of 3.17 to the region telomeric of D18S1153 on chromosome 18p.