Gout, Urate, and Crystal Deposition Disease

The diagnosis of crystal-induced arthritis is routinely established by synovial fluid analysis. However, a synovial effusion is not always present, fluid aspiration is not always possible or practical, and synovial fluid analysis is occasionally subject to false negative results. When there is a high suspicion of crystal-induced arthritis, but crystals are not identified in the synovial fluid, a biopsy of the synovium in search of crystals can assist in making a diagnosis. In this manuscript, we review the utility of ultrasound-guided needle biopsy of synovial tissue in the identification of crystal-induced arthritis, briefly describe the procedure, and recommend best practices for specimen handling and tissue processing.

For the 16th Anniversary this year, the ECN workshop is again held in downtown Paris. Every year the ECN workshop offers a unique opportunity for clinicians and researchers interested in crystals, inflammation, and crystal-induced diseases, including gout, to present their latest results and discuss novel concepts.

Calcium pyrophosphate deposition (CPPD) disease is a consequence of the immune response to the pathological accumulation of calcium pyrophosphate (CPP) crystals within joints. This clinically heterogeneous condition can cause significant disability, yet its management remains poorly defined. New discoveries are reshaping the therapeutic landscape beyond conventional anti-inflammatory agents—which remain the cornerstone of care—justifying this review on current standard of care and treatment advances in CPPD disease. We first address the two theoretical management goals, namely inflammation control and crystal dissolution—with attempts to address the latter having failed thus far. We then summarize the evidence supporting conventional anti-inflammatory treatments and review insights into the pathophysiology of CPPD disease, which are driving the development of novel therapeutic strategies. These include the current use of biologics (IL-1 and IL-6 inhibitors) to control inflammation and highlight the need to explore new pathways to inhibit crystal formation (e.g., selective NPP1 blockers). We present the treatments in the development pipeline for CPPD disease (including JAK inhibitors), and the therapies currently undergoing clinical trials in gout for which findings could be extended to CPPD disease given their shared pathophysiology (e.g., NLRP3 inhibitors). To support and improve research on CPPD disease treatments, clinical trial design needs to be standardized, incorporating the recent ACR/EULAR classification criteria for accurate diagnosis, careful phenotypic stratification to ensure homogeneous patient groups (although this point requires consensus), and validated core outcome domains currently being developed by the OMERACT.