Of all of the PADs, PAD4 is of specific interest because of its importance in innate immunity and its putative role in a variety of pathogenic states, including autoimmune diseases, such as rheumatoid arthritis (RA), multiple sclerosis (MS), ulcerative colitis (UC), and systemic lupus erythematosus (SLE), and other inflammatory conditions, such as sepsis and thrombosis (Jones et al., 2009). Here, PADI4 is linked to rheumatoid arthritis.