Because the two positive SNPs associated with HD are in the first haplotype block, which covers the 5′ flanking region of GRM3 (Fig. 3), the haplotypes of six SNPs (rs274618, rs274622, rs1990040, rs13242038, rs724226, and rs2189814) in this block were further evaluated to determine whether they affect the risk of HD. This evidence concerns the gene GRM3 and Huntington disease.