PRTN3 and rheumatoid arthritis: However, this MR analysis (175) only analyzed the causal association from ANM to RA, but not the association from RA to ANM, and it was conducted utilizing overall RA (a majority of which are seropositive RA, >85%) without identifying disease subsets distinguished by the presence/absence of anti-citrullinated peptide antibodies (ACPA) or rheumatic factors.