A connection discovered between spondyloarthritis and inflammatory bowel disease
Spondyloarthritis and IBDs* share a specific intestinal dysbiosis, characterized by overrepresentation by Ruminococcus gnavus.
Spondyloarthritis is a multifactorial disease associated with joint inflammation and non-joint disorders like psoriasis and inflammation in the eye (uveitis) and gut (IBD). Several genes have been identified among the risk factors, including HLA-B27 and several genes that predispose people to IBD. In contrast with genetic factors, potential environmental factors, such as a disruption in the intestinal microbiota, suspected of occurring in chronic inflammation, have been understudied.
To try to understand if specific dysbiosis is associated with spondyloarthritis, French researchers compared the intestinal microbiota of spondyloarthritis patients to rheumatoid arthritis patients and healthy controls. Although the microbiota of the two patient groups presented a dysbiosis characterized by reduced bacterial diversity, only the patients with spondyloarthritis and a history of IBD presented a level of Ruminococcus gnavus which was 2 to 3 times higher than the normal level, during the inflammatory phase of their disease. The researchers also noted differences in the composition of the microbiota compared with the healthy controls, depending on whether or not they carried the HLA-B27 gene.
The gene may therefore influence the composition of the intestinal microbiota, making dysbiosis where R. gnavus is in excess more likely, the researchers suggest. According to the researchers, this dysbiosis is specific to spondyloarthritis, and the pro-inflammatory nature of the bacteria would explain the associated IBDs.
*IBD: Inflammatory bowel disease
Breban M, Tap J, Leboime A, et al. Faecal microbiota study reveals specific dysbiosis in spondyloarthritis. Ann Rheum Dis 2017;76:1614–1622.