Furthermore, because haplotypes formed by rs6269, rs4633, rs4818, and rs4680 of COMT gene constituted central COMT locus haploblock that is associated with pain response15, we examined whether combinations of alleles (haplotypes) that were formed by the aforementioned four SNPs of COMT affect the susceptibility to pain in patients with PD. The gene discussed is COMT; the disease is Parkinson disease.