IKZF3 is a transcription factor located within a T1D susceptibility locus at 17q12 (Barrett et al., 2009) and overlaps susceptibility loci for ulcerative colitis, Crohn’s disease, primary billiary cirrhosis and rheumatoid arthritis (Jostins et al., 2012; Liu et al., 2012; Stahl et al., 2010). Here, IKZF3 is linked to rheumatoid arthritis.