PRTN3 and rheumatoid arthritis: Based on data from international registries, systematic reviews and meta-analyses, rheumatoid factor (RF) and/or anti-citrullinated protein antibody (ACPA, of which the presence and levels are frequently defined by anti-cyclic citrullinated peptide [anti-CCP] antibody) could be useful biomarkers for choosing B-cell depleting therapy with rituximab as a second-line treatment in RA patients who have failed the first biologic agent [8].