Rheumatoid arthritis (RA) is an inflamed chronic autoimmune disease in which genetics and environment are the most common causative factors. Peptidyl arginine deiminase type IV (PADI4) is an enzyme responsible for the posttranslational conversion of arginine residues into citrulline. Real-time polymerase chain reaction (RT-PCR) is a specific technique was used to determine gene polymorphism. One hundred twenty three patients molecularly confirmed with RA and sixty healthy control subjects were recruited. By applying the logistic regression analysis, some alleles and genotypes were associated with susceptibility to RA. Under the allelic model, C allele frequency was significantly increased in RA patients compared to control (58.5 vs. 46.7%; p = 0.034). The odds ratio (OR) of such difference was 1.61 (95% CI: 1.04 – 2.50). Under the dominant model, TC+CC genotype frequency was higher in patients than in control (82.1vs. 65.5%; OR = 2.47; 95% CI: 1.23 – 4.97; p = 0.015). Under the codominant model, frequency of the heterozygous genotype TC was significantly increased in patients compared to control (47.1 vs. 36.7%; OR = 2.52; 95% CI: 1.17 – 5.41; p = 0.028). The results revealed the role of the rs11203367 variant of padi4 gene in susceptibility to RA in Iraqi patients.
