REL and systemic lupus erythematosus: Some of these genes have been described to be shared with other related diseases, such as AS, inflammatory bowel disease (IBD), RA or systemic lupus erythematosus (SLE) (Figure 1), being the most prominent genes: ERAP1, ERAP2, IL23A, IL23R, REL, RUNX3, STAT4, TLR4, TNIP1, TRAF3IP2, TYK2.