In 2015, Dennis McGonagle et al. proposed a concept of "MHC-I-opathy," including Behçet disease and several clinically distinct spondyloarthropathies—all associated with MHC-I alleles, such as HLA-B*51, HLA-B*27, HLA-C*0602, or epistatic endoplasmic reticulum aminopeptidase 1(ERAP1) interaction [12]. Here, ERAP1 is linked to Behcet disease.