PRTN3 and rheumatoid arthritis: Interestingly, Jian et al. reported that the risk of CS on both ACPA-positive and -negative RA development increased only with the use of inhaling cigarettes but not nicotine-contained chewed cigarettes (OR, 1.0; 95% CI, 0.8–1.2), suggesting that nicotine is not directly involved in RA pathogenesis [160].