Since the absence of anti-CarP Abs has been observed in patients with other inflammatory rheumatic diseases as well as in healthy individuals [52], its occurrence can be considered specific for RA to a limited extent, but as the results of a large study by Lo et al. recently showed, in which more than 4.6 million peptides were analyzed, there are more opportunities to identify unexplored ACPA epitopes that are further specific for RA [44]. The gene discussed is PRTN3; the disease is rheumatoid arthritis.