Among the large number of studied SNPs, it was found that several SNPs in different genes might control the susceptibility of PV, including TNFA (rs361525, rs1800629, rs1800629), IL10 (rs1800871, rs1800896, rs1800871, and rs1800872), IL6 (rs1800795), CTLA4 (rs231775), ICOS (rs10932029), CD86 (rs1129055), DSG3 (rs8085532, rs3911655, rs3848485, rs3794925, rs1466379), ST18 (rs2304365, rs17315309) and TAP2 (rs7454108), probably in a population-specific manner.
A fine-mapping analysis of PV risk in the major histocompatibility complex region showed three independent variants predisposed to PV using stepwise analysis: HLA-DRB1*14:04 (P = 2.47 × 10<sup>-38</sup>, odds ratio = 6.28), rs7454108 at the TAP2 gene (P = 2.78 × 10<sup>-12</sup>, odds ratio = 3.25), and rs1051336 at the HLA-DRA gene (P = 3.06 × 10<sup>-6</sup>, odds ratio = 0.33).
Two PVTAP2 risk alleles were identified (TAP2*C and TAP2*D), the frequency of which was estimated to be 37.8% in the patients and 5.3 % in the controls.