Exclusion of linkage between dyschromatosis symmetrica hereditaria and chromosome 9

Dyschromatosis symmetrica hereditaria (DSH) is an autosomal dominant pigmentary disorder, first reported by Toyama in 1910. It is characterized by a mixture of hypopigmented and hyperpigmented macules of various sizes on the backs of the hands and feet. The disease gene of DSH and its chromosomal localization have not yet been identified. A family with DSH and idiopathic torsion dystonia (ITD), a rare neurological disease, was recently reported. Therefore, we speculated that there was a linkage between the DSH gene and the ITD gene, named DYT1 and localized on chromosome 9, and performed linkage analysis between DSH and microsatellite markers on chromosome 9 in three Japanese DSH families (36 patients in total). We obtained a LOD score of < -2 over the whole region of chromosome 9 encompassing DYT1. Thus, we conclude that there is no linkage between DSH and DYT1 as well as any region of chromosome 9.