PRTN3 and rheumatoid arthritis: The aim of this study was to undertake an unsupervised proteomic analysis of the circulating RA citrullinome, and determine the consequences of citrullination in RA.<h4>Methods</h4>Citrullinated serum proteins were isolated and measured by mass spectrometry from 10 anti-citrullinated protein antibody (ACPA) positive RA patients and 10 controls.