Primary torsion dystonia (PTD) is a clinically and genetically heterogeneous group of movement disorders, usually inherited in an autosomal dominant fashion with reduced penetrance. The DYT1 gene on chromosome 9q34 is responsible for most cases of early limb-onset PTD. Two other PTD loci have been mapped to date. The DYT6 locus on chromosome 8 is associated with a mixed phenotype, whereas the DYT7 locus on chromosome 18p is associated with adult onset focal cervical dystonia. Several families have been described in which linkage to the known PTD loci have been excluded. We identified a large Italian PTD family with 11 definitely affected members. Phenotype was characterized by prominent cranial-cervical and upper limb involvement and mild severity. A genome-wide search was performed in the family. Linkage analysis and haplotype construction allowed us to identify a novel PTD locus (DYT13) within a 22 cM interval on the short arm of chromosome 1, with a maximum lod score of 3.44 between the disease and marker D1S2667.
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