Autoantibodies to protein-arginine deiminase (PAD) 4 in rheumatoid arthritis: immunological and clinical significance, and potential for precision medicine.

: The protein-arginine deiminase (PAD) 4 enzyme plays an important role in the pathogenesis of rheumatoid arthritis (RA) and also represents an antigenic target. Anti-PAD4 antibodies can be present in RA and are associated with specific clinical features. : This review aims to analyze the current knowledge and recent findings on anti-PAD4 antibodies in RA and their clinical and immunological significance. : Anti-PAD4 antibodies are not currently used in clinical practice for the management of RA. Nevertheless, there is growing evidence of their relevance in RA, and of their potential utility to improve diagnosis, patient stratification, and prognosis.