Sporadic focal dystonia in northwest Germany: molecular basis on chromosome 18p.

Idiopathic focal dystonia (IFD) is the most common form of idiopathic torsion dystonia in the Euroamerican population, with a prevalence of about 30 per 100,000. Although most patients claim a negative family history, we recently mapped this syndrome to chromosome 18p as an autosomal dominant trait in Family K from Northwest Germany. We now have investigated sporadic patients with IFD from the same geographic area both clinically and molecularly with chromosome 18p markers. The data indicate that most of these apparently sporadic patients have inherited the same mutation as Family K from a common ancestor and, in fact, owe their disease to autosomal dominant inheritance at low penetrance. The data also indicate that this dystonia mutation (DYT7) is the predominant cause of IFD, at least in this area of Northwest Germany, and that its location can be narrowed from a 30- to a 6-centimorgan region close to marker D18S1098.