Seemingly contrasting genetic backgrounds in anti-citrullinated-protein antibody (ACPA)-positive and ACPA-negative rheumatoid arthritis (RA) support the notion that these are in fact two distinct... Show moreSeemingly contrasting genetic backgrounds in anti-citrullinated-protein antibody (ACPA)-positive and ACPA-negative rheumatoid arthritis (RA) support the notion that these are in fact two distinct disease subsets, with different underlying pathogenesis, that might need tailored treatment strategies. Show less