The genes that encode the ERAP proteins, ERAP1 and ERAP2, are located adjacent to each other on 5q15 (Hutchinson et al. 2021; Paladini et al. 2020) and both have been implicated in the development of multiple autoimmune diseases, including Bechet’s disease, birdshot uveitis, ankylosing spondylitis (AS) and inflammatory bowel disease (IBD) (Hutchinson et al. 2021; López de Castro 2018; Yao et al. 2019). This evidence concerns the gene ERAP2 and inflammatory bowel disease.