Interestingly, the pathogenesis of autoimmune/autoinflammatory disorders, such as AS, BD, BSCR and Ps, seems to arise, at least in part, by the epistatic interaction between ERAP1 and a HLA class I molecules (HLA-B*27, HLA-B*51, HLA-A*29:02 and HLA-C*06:02, respectively). The gene discussed is HLA-B; the disease is birdshot chorioretinopathy.