PADI4 polymorphisms and the functional haplotype are associated with increased rheumatoid arthritis susceptibility: A replication study in a Southern Mexican population.

Rheumatoid arthritis (RA) is a common autoimmune disease with a complex genetic background. The peptidyl arginine deiminase type IV (PADI4) gene has been associated with RA susceptibility in several populations. We addressed the relationship between three exonic PADI4 gene single nucleotide polymorphisms (SNPs) PADI4_89 (rs11203366), PADI4_90 (rs11203367) and PADI4_92 (rs874881) and related haplotypes with RA in a population from Southern México. This study included 200 RA patients and 200 control subjects. The SNPs were evaluated using the polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) technique, and antibodies to cyclic citrullinated peptides (anti-CCP) were measured by enzyme-linked immunosorbent assay (ELISA). In this population, the minor alleles of PADI4_89∗G, PADI4_90∗T and PADI4_92∗G gene polymorphisms were associated with RA susceptibility (OR=1.34, p=0.04; OR=1.35, p=0.03; OR=1.34, p=0.04; respectively). The GTG haplotype was also significantly associated with RA (OR=2.27 95%CI=1.18-4.41; p=0.008), but did not show association with levels of anti-CCP antibodies and clinical parameters. In conclusion, our replication study in a Southern Mexican population suggests that PADI4 individual polymorphisms and the related susceptibility haplotype (GTG) are also genetic risk markers for RA.