This study aims to investigate the association of rs11203366, rs11203367, rs874881, rs2240340, and rs1748033 polymorphisms of protein arginine deiminase type 4 (PADI4) gene with the risk of rheumatoid arthritis (RA) through a meta-analysis that was followed with a bioinformatics approach. The data were collected from reputable articles and underwent quantitative analysis, followed by in silico analysis using some bioinformatics tools. The results showed that rs874881 polymorphism in Latino (G vs. C: OR= 1.35, 95%CI= 1.11-1.65, P= 0.003; GG+CG vs. CC: OR= 2.02, 95%CI= 1.41-2.89, P= 0.0001; CG vs. CC+GG: OR= 1.38, 95%CI= 1.04-1.83, P= 0.027; GG vs. CC: OR= 2.09, 95%CI= 1.35-3.23, P= 0.001; CG vs. CC: OR= 1.98, 95%CI= 1.36-2.87, P= 0.00033) and rs1748033 in Caucasian population (T vs. C: OR= 1.25, 95%CI= 1.07-1.45, P= 0.005; TT vs. CT+CC: OR= 1.34, 95%CI= 1.09-1.64, P= 0.005, TT+CT vs. CC: OR= 1.26, 95%CI= 1.09-1.44, P= 0.001; TT vs. CC: OR= 1.59, 95%CI= 1.13-2.23, P= 0.007; CT vs. CC: OR= 1.20, 95%CI: 1.04-1.39, P= 0.015) are associated with increased risk of RA. Also, rs11203366 (G vs. A: OR= 1.46, 95%CI= 1.19-1.78, P= 0.0002), GG vs. AG+AA: OR= 1.42, 95%CI= 1.01-2.01, P= 0.043; GG+AG vs. AA: OR= 2.03, 95%CI= 1.45-2.86, P= 0.00004; GG vs. AA: OR= 2.29, 95%CI= 1.49-3.51, P= 0.0002; AG vs. AA: OR= 1.93, 95%CI= 1.35-2.76, P= 0.0003) and rs11203367 (T vs. C: OR= 1.50, 95%CI= 1.23-1.83, P= 0.00007; TT vs. CT+CC: OR= 1.56, 95%CI= 1.12-2.18, P= 0.009; TT+CT vs. CC: OR= 2.02, 95%CI= 1.43-2.84, P= 0.00007, TT vs. CC: OR= 2.43, 95%CI= 1.59-3.71, P= 0.0004; CT vs. CC: OR= 1.86, 95%CI= 1.30-2.68, P= 0.0007) had an impact in the Latino population. Bioinformatics tools showed the effect of these polymorphisms on gene function. These findings suggest that rs11203366, rs11203367, rs874881 and rs1748033 polymorphisms may be genetic risk factors for RA. Also, differences between populations suggest that ethnicity may play an important role in the effect of these polymorphisms on RA risk.
