HLA-C and inflammatory bowel disease: From a pathophysiological aspect, several genetic loci related to immune function, cytokine signalling and major histocompatibility complex (MHC) proteins have been associated with either SpA and IBD, with plenty of them being common for both diseases.21 Moreover, environmental stresses such a smoking and, particularly, intestinal dysbiosis have been implicated in the pathogenesis of both IBD and SpA, while mechanical forces are related solely to SpA.16,22,23