Microparticles (MPs) are small membrane-bound vesicles that arise from activated and dying cells and enter the blood to display pro-inflammatory and pro-thrombotic activities. MPs are 0.1-1.0 μm in size and incorporate nuclear, cytoplasmic and membrane molecules as they detach from cells. This process can occur with cell activation as well as cell death, with particles likely corresponding to blebs that form on the cell surface during apoptosis. To measure particle expression, flow cytometry allows determination of particle numbers based on size as well as surface markers that denote the cell of origin; platelet MPs are usually the most abundant type in blood. As shown in in vitro and in vivo systems, MPs can promote inflammation and thrombosis resulting from their content of cytokines like IL-1 and pro-coagulant molecules like tissue factor. Certain particle types can be anti-inflammatory, however, suggesting a range of immunomodulatory activities depending on the cell of origin. Studies on patients with a wide range of rheumatic disease show increased MP numbers in blood, with platelet and endothelial particles associated with vascular manifestations; increased numbers of particles also occur in the joint fluid where they may drive cytokine production and activate synoviocytes. In autoimmune diseases such as SLE and RA, MPs may also contribute to disease pathogenesis by the formation of immune complexes. MPs thus represent novel subcellular structures that can impact on the pathogenesis of rheumatic disease and serve as biomarkers of underlying cellular disturbances.

Although classic gout is still most commonly seen, the disease can manifest as with a wide array of presentations. It is likely that such atypical presentations are a result of a complexity of reasons. When presented with a diagnostic challenge in a patient with gout, the clinician should be aware of unusual manifestations of gout and consider it in the differential.

B-cell-directed therapy-the use of agents that eliminate B cells or block cytokines important for B-cell function-is emerging as a promising approach to the treatment of rheumatic disease. Target diseases, including systemic lupus erythematosus (SLE), display diverse patterns of autoantibody production and aberrant activation of B cells. Despite the success of this general approach, the mechanisms by which B-cell-directed therapy ameliorates disease, and the role of autoantibodies as biomarkers of clinical response remain unclear. Importantly, although B-cell-directed therapy can reduce the production of some autoantibodies, the effects can be variable and heterogeneous, probably reflecting the critical (but ill-defined) roles of different B-cell and plasma cell populations in autoantibody production. Future studies during clinical trials of these agents are needed to define which B-cell and autoantibody populations are affected (or ought to be), and to discover informative biomarkers of clinical response that can be used to advance this therapeutic approach.