Whole-body MRI in inflammatory arthritis - Systematic literature review and first steps towards standardization and an OMERACT scoring system

Objective: Whole-body magnetic resonance imaging (WB-MRI) is a relatively new technique that can enable assessment of the overall inflammatory status of people with arthritis, but standards for image acquisition, definitions of key pathologies, and a quantification system are required. Our aim was to perform a systematic literature review (SLR) and to develop consensus definitions of key pathologies, anatomical locations for assessment, a set of MRI sequences and imaging planes for the different body regions, and a preliminary scoring system for WB-MRI in inflammatory arthritis. Methods: An SLR was initially performed, searching for WB-MRI studies in arthritis, osteoarthritis, spondyloarthritis, or enthesitis. These results were presented to a meeting of the MRI in Arthritis Working Group together with an MR image review. Following this, preliminary standards for WB-MRI in inflammatory arthritides were developed with further iteration at the Working Group meetings at the Outcome Measures in Rheumatology (OMERACT) 2016. Results: The SLR identified 10 relevant original articles (7 cross-sectional and 3 longitudinal, mostly focusing on synovitis and/or enthesitis in spondyloarthritis, 4 with reproducibility data). The Working Group decided on inflammation in peripheral joints and entheses as primary focus areas, and then developed consensus MRI definitions for these pathologies, selected anatomical locations for assessment, agreed on a core set of MRI sequences and imaging planes for the different regions, and proposed a preliminary scoring system. It was decided to test and further develop the system by iterative multireader exercises. Conclusion: These first steps in developing an OMERACT WB-MRI scoring system for use in inflammatory arthritides offer a framework for further testing and refinement

Enthesitis: from pathophysiology to treatment

Entheses are the insertion sites of tendons and ligaments to the bone surface and are essential structures for locomotion. Inflammation of the entheses (enthesitis) is a key feature of psoriatic arthritis and spondyloarthritis. To date, our conceptual understanding of enthesitis remains limited. This Review provides an insight into the pathophysiology of enthesitis, addressing the role of biomechanics, prostaglandin E2-mediated vasodilation and the activation of innate immune cells in the initiation phase of enthesitis, as well as the role of entheseal IL-23-responsive cells that augment inflammation by producing pro-inflammatory mediators such as IL-17A, IL-22 and TNF. In addition, the molecular steps that translate inflammation into resident tissue responses, resulting in new bone formation, are discussed. The second part of the article summarizes the clinical features of enthesitis, and the role of clinical and imaging instruments in detecting enthesitis are discussed together with their challenges and limitations. Finally, the Review summarizes the current treatment possibilities for enthesitis based on the aforementioned pathophysiological concepts, focusing on the role of cytokine-blocking agents

Focal bone involvement in inflammatory arthritis: the role of IL17

Conditions such as rheumatoid arthritis (RA) and spondyloarthritis (SpA, such as psoriatic arthritis, PsA, and ankylosing spondylitis, AS) are characterized by an imbalance between osteoclast (OC) bone resorption and osteoblast (OB) bone formation. The two conditions present substantial differences in bone involvement, which is probably related to the different expression of IL17 and TNF\u3b1, two cytokines that strongly promote osteoclastogenesis and focal bone erosions. TNF\u3b1 is the major inflammatory cytokine in RA. It acts by both triggering OC bone erosion via the RANK-RANKL system, and suppressing OB bone formation through the overexpression of DKK1, a powerful inhibitor of the WNT bone anabolic signaling pathway. Differing from TNF\u3b1, IL17 promotes also osteogenesis, particularly at inflamed sites undergoing mechanical stress, such as entheses. Therefore, in RA, where overexpression of TNF\u3b1 is higher than IL17, OC bone resorption largely prevails upon bone formation. In PsA and AS, the prevailing inflammatory cytokine is IL17, which promotes also osteogenesis. Given the prevalent involvement of entheses poor of OC, excess bone formation may even prevail over excess bone resorption. The results of clinical trials support the different pathophysiology of bone involvement in chronic arthritis. Inflammation control through anti-TNF\u3b1 agents has not resulted in incomparable effects on radiographic progression and excess bone formation in both AS and PsA. Clinical trials investigating IL17 inhibitors, such as secukinumab, in patients with psoriatic disease are underway. The preliminary results on inflammation and symptoms appear positive, while long-term studies are required to demonstrate an effect on excess bone formation