PADI4 and Arthritis: The GTTC haplotype in PADI4 was associated with an increased risk of developing arthritis (OR = 1.40, 95% CI = 1.12–1.74, p = 0.018) while three haplotypes (GTCG, ACTC, and ACTG) were associated with decreased risk (OR = 0.12 to 0.65, [p < 0.05]).