As smoking is also regarded as an important risk factor for ACPA-positive RA in particular [12,31], and PADI SNPs have been suggested to interact with smoking in the pathogenesis of RA [30,32], we examined the associations between SNPs in PADI2 in relation to anti-CCP status and smoking status in the subgroup of patients with self-reported periodontitis. This evidence concerns the gene PADI2 and periodontitis.