Purpose of review: Microscopic polyangiitis is defined within the context of primary systemic vasculitis. The presentation and management of renal involvement in microscopic polyangiitis is discussed, with emphasis on prognosis and outcomes. Potential roles of newer therapies are reviewed.
Recent findings: The histological features of kidney disease in microscopic polyangiitis have been associated with clinical presentation and renal outcome. The predictive value of antineutrophil cytoplasm antibody positivity after induction therapy has been highlighted. Plasma exchange improves renal recovery rates in severe presentations in a randomized trial. Initial results with rituximab have indicated that the B cell is an important therapeutic target in vasculitis and that B-cell depletion has the potential to replace immune suppressive treatment in the future.
Summary: Microscopic polyangiitis is a subgroup of primary systemic vasculitis, but diagnostic problems remain with antineutrophil cytoplasm antibody-negative cases and in those without kidney disease. Plasma exchange has a confirmed place in therapy. The poor outcomes of many patients indicate safer, more effective therapies are required. Improved biomarkers are needed to assist in drug selection, monitoring and prognosis.