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Idiopathic torsion dystonia is a clinically and genetically heterogeneous movement disorder. A GAG deletion at position 946 of the DYT1 gene was the first mutation found, in early-onset dystonia, with an autosomal dominant transmission an d reduced penetrance. Only 5 mutation carriers were identified, 4 of whom were part of a group of 10 patients with generalized dystonia. Onset was between ages 5 and 12 years as in typical early-onset dystonia. All 4 patients had cranial muscle involv ement, which is atypical for DYT1 mutation carriers. One had segmental dystonia. Molecular analysis of relatives in 2 families demonstrated that the lack of family history was due to reduced penetrance. For accurate diagnosis and genetic counseling, sc reening for the SYT1 deletion is of great interest in cases with generalized dystonia without a family history. In other cases, positive results are rare. |
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