A novel locus for inherited myoclonus-dystonia on 18p11

Objective: Inherited myoclonus-dystonia (IMD) is a new term for an autosomal dominant disorder characterized by myoclonus and dystonia. Recently, IMD was linked to a region on chromosome 11q23 with two different mutations identified in the D2 dopamine receptor gene and linked to chromosome 7q with five different loss-of-function mutations identified in the E-sarcoglycan gene. Methods: These two regions and genes were excluded in a large Canadian family with IMD in whom 13 individuals are affected. A 25-cM genome scan of this large family with 32 individuals was performed. Results: Two-point linkage analysis revealed a maximum lod score of 3.5 (recombination fraction 0.00; affected only) for the microsatellite marker GATA185C06-18 and a multipoint lod score of 3.9 across the 18p11 region. Haplotype analysis demonstrates that all the affected individuals shared a common haplotype between markers D18S1132 and D18S843 that defines the disease gene within a span of 16.9 cM. Conclusions: These findings indicate that a novel IMD gene exists on chromosome 18p11.