Article here:Background
Enteropathic arthropathies comprise a collection of rheumatologic conditions that share a link to GI pathology. These conditions include reactive (ie, infection-related) arthritis caused by bacteria (eg, Shigella, Salmonella, Campylobacter, Yersinia species, Clostridium difficile), parasites (eg, Strongyloides stercoralis, Taenia saginata, Giardia lamblia, Ascaris lumbricoides, Cryptosporidium species), and spondyloarthropathies associated with inflammatory bowel disease (IBD).
Other conditions and disorders include intestinal bypass (jejunoileal), arthritis, celiac disease, Whipple disease, and collagenous colitis.
Pathophysiology
The precise causes of enteropathic arthropathies are unknown. Inflammation of the GI tract may increase permeability, resulting in absorption of antigenic material, including bacterial antigens. These arthrogenic antigens may then localize in musculoskeletal tissues (including entheses and synovium), thus eliciting an inflammatory response. Alternatively, an autoimmune response may be induced through molecular mimicry, in which the host's immune response to these antigens cross-reacts with self-antigens in synovium.
Of particular interest is the strong association between reactive arthritis and HLA-B27, an HLA class I molecule. A potentially arthrogenic, bacterially derived antigen peptide could fit in the antigen-presenting groove of the B27 molecule, resulting in a CD8+ T-cell response. HLA-B27 transgenic rats develop features of enteropathic arthropathy with arthritis and gut inflammation.
http://www.emedicine.com/med/topic3098.htm