PRTN3 and rheumatoid arthritis: An interplay between genetics (>100 loci), environmental factors (eg, cigarette smoking and occupational exposure to silica) and alterations in the mucosal microbiome can contribute to the development of RA.6 7 Clinical RA is preceded by an asymptomatic preclinical breach of tolerance to citrullinated self-peptides, activation of autoreactive T cells and production of anticitrullinated peptide-specific antibodies (ACPA).