Antineutrophil cytoplasmic antibody (ANCA) vasculitis: pathophysiology, diagnosis, and the evolving treatment landscape.

The antineutrophil cytoplasmic antibody (ANCA) vasculitides include several closely related, often severe, multisystem autoimmune diseases characterized by antibodies against serine proteinase 3 (PR3) or myeloperoxidase. Loss of tolerance to these antigens triggers a cascade of events, beginning with the priming of neutrophils by proinflammatory cytokines and complement activation, translocation of ANCA-specific antigens to the plasma membrane, neutrophil hyperactivation, and further activation of the alternative complement pathway, leading to tissue damage and the clinical manifestations of ANCA vasculitis. Due to the heterogeneity in presentation of these diseases, diagnosis is often substantially delayed, leading to poor outcomes.