Objective Dysbiosis of the intestinal microbiota has been widely established in inflammatory bowel disease (IBD). There is significant clinical and genetic overlap between spondyloarthritis (SpA) and IBD, and up to 50% of all patients with SpA exhibit microscopic signs of bowel inflammation, often bearing particular resemblance to early Crohn's disease, a subtype of IBD. This study was undertaken to assess the relationship between intestinal microbial composition, gut histology, and disease activity markers in SpA. Methods Gene analysis by 16S ribosomal RNA amplicon sequencing was used to compare the microbial composition in ileal and colonic biopsy specimens from 27 patients with SpA (14 with microscopic bowel inflammation, 13 without) and 15 healthy control subjects (ileal samples from all 15 subjects and colonic samples from 6). Spearman's rank correlation tests were used to assess correlations of the microbial composition with disease activity measures. Results The intestinal inflammation status (histologically normal versus acute or chronic inflammation) was strongly associated with the mucosal microbiota profile of patients with SpA. In inflamed biopsy tissue, the detected bacterial community composition clustered separately from that in noninflamed biopsy tissue (P < 0.05 by permutational multivariate analysis of variance, using hierarchical clustering on Bray–Curtis distances). Interestingly, abundance of the genus Dialister was found to be positively correlated with the Ankylosing Spondylitis Disease Activity Score (Spearman's rho = 0.62, false discovery rate–corrected q < 0.01). This finding was further supported by the low frequency of Dialister observed in noninflamed ileal and colonic biopsy tissue from patients with SpA and healthy controls. Conclusion These findings demonstrate a significant difference in the intestinal microbial composition in patients with SpA who have microscopic gut inflammation compared to those without microscopic gut inflammation. Moreover, Dialister may represent a potential microbial marker of disease activity in SpA.

Dysregulated IL-23/IL-17 responses have been linked to psoriatic arthritis and other forms of spondyloarthritides (SpA). RORγt, the key Thelper17 (Th17) cell transcriptional regulator, is also expressed by subsets of innate-like T cells, including invariant natural killer T (iNKT) and γδ-T cells, but their contribution to SpA is still unclear. Here we describe the presence of particular RORγt+T-betloPLZF− iNKT and γδ-hi T cell subsets in healthy peripheral blood. RORγt+ iNKT and γδ-hi T cells show IL-23 mediated Th17-like immune responses and were clearly enriched within inflamed joints of SpA patients where they act as major IL-17 secretors. SpA derived iNKT and γδ-T cells showed unique and Th17-skewed phenotype and gene expression profiles. Strikingly, RORγt inhibition blocked γδ17 and iNKT17 cell function while selectively sparing IL-22+ subsets. Overall, our findings highlight a unique diversity of human RORγt+ T cells and underscore the potential of RORγt antagonism to modulate aberrant type 17 responses.

IntroductionMicroscopic bowel inflammation is present in up to 50% of patients with spondyloarthritis (SpA) and is associated with more severe disease. Currently no reliable biomarkers exist to identify patients at risk. Calprotectin is a sensitive marker of neutrophilic inflammation, measurable in serum and stool.ObjectivesTo assess whether serum and faecal calprotectin in addition to C-reactive protein (CRP) can be used to identify patients with SpA at risk of microscopic bowel inflammation.MethodsSerum calprotectin and CRP were measured in 125 patients with SpA. In 44 of these patients, faecal samples were available for calprotectin measurement. All 125 patients underwent an ileocolonoscopy to assess the presence of microscopic bowel inflammation.ResultsMicroscopic bowel inflammation was present in 53 (42.4%) patients with SpA. Elevated serum calprotectin and CRP were independently associated with microscopic bowel inflammation. Faecal calprotectin was also significantly higher in patients with microscopic bowel inflammation. Patients with CRP and serum calprotectin elevated had a frequency of bowel inflammation of 64% vs 25% in patients with low levels of both. When either CRP or serum calprotectin was elevated, the risk was intermediate (40%) and measuring faecal calprotectin provided further differentiation. Hence we suggest a screening approach where initially serum calprotectin and CRP are assessed and, if necessary, faecal calprotectin. The model using this scenario provided an area under the ROC curve of 74.4% for detection of bowel inflammation.ConclusionsCalprotectin measurements in stool and serum, in addition to CRP, may provide a promising strategy to identify patients with SpA at risk of bowel inflammation and could play a role in overall patient stratification.

ObjectivesBone marrow oedema (BMO) on MRI of sacroiliac joints (SIJs) represents a hallmark of axial spondyloarthritis (SpA), yet such lesions may also occur under augmented mechanical stress in healthy subjects. We therefore sought to delineate the relationship between pregnancy/delivery and pelvic stress through a prospective study with repeated MRI. Results were matched with maternal, child and birth characteristics.MethodsThirty-five women underwent a baseline MRI-SIJ within the first 10 days after giving birth. MRI was repeated after 6 months and, if positive for sacroiliitis according to the Assessment of SpondyloArthritis International Society (ASAS) definition, after 12 months. BMO and structural lesions were scored by three trained readers using the Spondyloarthritis Research Consortium of Canada (SPARCC) method.ResultsSeventy-seven per cent of the subjects (27/35) displayed sacroiliac BMO immediately postpartum, 60% fulfilled the ASAS definition of a positive MRI. After 6 months, 46% of the subjects (15/33) still showed BMO, representing 15% (5/33) with a positive MRI. After 12 months, MRI was still positive in 12% of the subjects (4/33). Few structural lesions were detected. Intriguingly, in this study, the presence of BMO was related to a shorter duration of labour and lack of epidural anaesthesia.ConclusionA surprisingly high prevalence of sacroiliac BMO occurs in women immediately postpartum. Our data reveal a need for a waiting period of at least 6 months to perform an MRI-SIJ in postpartum women with back pain. This study also underscores the importance of interpreting MRI-SIJ findings in the appropriate clinical context.

Vedolizumab therapy does not seem to show any efficacy in and might even induce arthritis and/or sacroiliitis. However, larger cohort studies are needed to provide information on the prevalence, the evolution and underlying mechanism.

A substantial proportion of healthy active individuals without any symptoms of back pain displayed bone marrow oedema lesions on MRI at baseline. However, MRI lesions did not increase significantly after 6 weeks of intensive physical training. Our study underscores the necessity to interpret MRI findings of the SIJs in the appropriate clinical context, even in a young active population.

Summary Background Spondyloarthritis is the most frequent extra‐intestinal manifestation of IBD. Aim To present simple strategies to identify and differentiate inflammatory joint pain in IBD patients. Methods A panel of Belgian gastroenterologists and rheumatologists developed seven algorithms for IBD patients with joint symptoms based on a Delphi exercise conducted between April and December 2016. Here, we focus on referral strategies for patients with chronic back pain (evidence‐based strategy), large joint monoarthritis, oligo‐ or polyarticular arthritis or arthralgia (based on expert opinion). We also present management tools for IBD patients with acute back pain and small joint monoarthritis (Supplementary file). Results The reported algorithm for IBD patients with chronic back pain uses basic clinical criteria to identify which patients should be referred to the emergency room (spondylodiscitis), physical medicine and rehabilitation (mechanical back pain) or rheumatologist (spondyloarthritis). IBD patients with large joint monoarthritis should be referred to emergency room if septic arthritis is suspected; in other patients, blood analyses and referral to a rheumatologist for articular puncture with evacuation of synovial fluid are recommended. The analysis of synovial fluid allows for identification of non‐inflammatory (e.g., osteoarthritis) and inflammatory (e.g., [pseudo]‐gout, peripheral spondyloarthritis and Borrelia burgdorferi arthritis) conditions. In patients with inflammatory oligoarticular or polyarticular arthralgia, erythrocyte sedimentation rate, concomitant therapies, anti‐nuclear factor and anti‐double‐stranded DNA antibody levels should be evaluated; in anti‐tumour necrosis factor‐treated patients, a drug‐induced lupus‐like syndrome should be considered. Conclusion We propose straightforward strategies for IBD patients with joint symptoms, which are specific enough to select initial treatment and referral pattern.

NCT01426815; Results.