Inflammatory bowel disease-related arthritis - clinical evaluation and possible role of cytokines

In inflammatory bowel disease (IBD), characterized by chronic mucosal inflammation, rheumatic abnormalities ranging from arthralgia to spondyloarthritis (SpA) are the most common extraintestinal manifestations. The pathogenesis of IBD-related arthritis is unclear. In this study, we search for clinical and immunological differences between patients with IBD-associated spondyloarthritis and IBD patients without SpA symptoms.

Patients with an established diagnosis of IBD, suffering from Leśniowski-Crohn disease (L-CD, n = 24) or ulcerative colitis (UC, n = 27), were enrolled in the study. Clinical evaluation of patients, based on medical history, blood tests, physical and radiological examinations, allowed two subgroups of patients to be established. One subgroup comprised patients fulfilling criteria for both IBD and SpA (IBD + SpA, n = 29), while the other included IBD patients with arthralgia only (IBD, n = 22). Serum concentrations of interleukins (IL-6, IL-10, IL-21, IL-22, IL-23) and interferon γ (IFN-γ) were measured by specific enzyme-linked immunosorbent assays (ELISA).

Patients with IBD + SpA were characterized by shorter disease duration (3 vs. 9 years), higher frequency of HLA-B27 positivity (60.7% vs. 4.5%) and uveitis (20.7% vs. 0%), compared with the IBD subgroup. The serum concentrations of C-reactive protein (CRP) and tested cytokines did not differ between IBD + SpA and IBD patients, or between L-CD and UC groups. However, in the IBD + SpA subgroup there was weak to moderate positive correlation between serum concentrations of CRP and several cytokines (IL-6, IL-21, IFN-γ), and additional moderate positive correlation between serum concentrations of IL-23 and clinical activity of SpA. By contrast, in IBD subgroup a strong inverse correlation between serum concentrations of Interleukin 23 and CRP was found.

IBD-related spondyloarthritis occurs relatively early, affects mostly HLA-B27(+) individuals, and is often accompanied by ocular involvement. In these patients several circulating cytokines are associated with systemic inflammation. IL-23 seems to be protective in IBD while detrimental in IBD-related spondyloarthritis.