Gut dysbiosis in Spondyloarthritis: Cause or effect?

Spondyloarthritis (SpA) is a group of chronic, inflammatory rheumatic diseases mainly affecting the axial skeleton. Although the pathogenesis of the disease remains elusive, alterations of intestinal microbial composition have been demonstrated in patients with SpA and associated with intestinal and systemic immune alterations. Substantial data have been published in recent years in ethnically different patient populations, demonstrating in a consolidated way the presence of alterations in the composition of the microbial flora in patients with SpA. It is not currently possible to establish whether these alterations are intrinsically inherent in the disease, for example, the effect of particular genes that confer susceptibility to the disease itself, or are a consequence of a more systemic inflammatory process that also involves the intestine. However, data deriving from animal models and studies on relatives of patients with SpA strongly suggest that these alterations might precede the onset of the disease. In this review, we will try to critically analyze studies on dysbiosis in SpA and animal models of SpA, analyzing their functional consequences and the impact of biotechnological therapies on intestinal bacterial composition.