Genomic imprinting and anticipation in idiopathic torsion dystonia.

Idiopathic torsion dystonia (ITD) is a dominantly inherited disorder with variable penetrance and expressivity. Factors affecting the penetrance of the ITD gene have not yet been identified. The present study used four published series of cases to test specific hypotheses regarding factors that could affect the expression of ITD. Among the combined 253 families, transmission of ITD did not depend on either the sex of the affected offspring or that of the transmitting parent. Furthermore, neither the specific type of dystonia manifested, the site at which clinical signs of dystonia first appeared, nor age of onset differed significantly as a function of the gender of the transmitting parent. However, in familial cases of later onset (age > or = 20 years), nearly all involved a transmitting mother. There is evidence for consistency of age of onset within the subset of Jewish families. Although anticipation effects are apparent, sampling bias cannot be ruled out.