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. This evidence concerns the gene IL23R and systemic lupus erythematosus.