IRF5 and rheumatoid arthritis: Interferon regulatory factor 5 (IRF5) polymorphism has been shown to be a risk factor for the development of SLE [1], [2], [3], [4], [5], rheumatoid arthritis (RA) [6], [7], [8], [9], multiple sclerosis (MS) [10], Sjögren's syndrome [11] and inflammatory bowel disease [12].