Several single nucleotide polymorphisms (SNPs) have been associated with rheumatoid arthritis (RA) such as peptidylarginine deiminase-4 (PADI4), osteopontin (OPN), and perforin (PRF1) genes. Thus, we aimed at analysing the influence of eight SNPs in these candidate genes on RA susceptibility and their association with laboratory and clinical features in terms of response to anti-TNF therapy.
We performed a case-control study on 377 Caucasian RA patients and 391 healthy, ethnicity-matched, population-based controls. All subjects were genotyped for PADI4_89/94, PADI4_92, PADI4_104, PADI4_100 in PADI4; -156G/GG and +1239A/C in OPN and A91V and N252S in PRF1 genes. The patients were stratified for shared epitope (SE) HLA-DRB1. rheumatoid factor (RF) and anti-citrullinated protein/peptide antibodies (ACPA) were analysed. The patients started anti-TNF treatment and they were evaluated at baseline and after 12 weeks. Disease activity was evaluated with DAS28 and response to treatment with EULAR criteria.
A statistically significant association between RA and OPN -156G/GG was found (p=0.023). SE was firmly confirmed to be associated with RA (OR=3.68; p<10-10). No other statistically significant association with clinical and laboratory features were observed.
For the first time, in an Italian cohort, we report the association between -156G/GG in OPN gene and RA susceptibility. Short-term response to anti-TNF therapy was not influenced by the genetic variants studied.