ANCA-associated vasculitis, adult

Antineutrophil cytoplasmic antibody (ANCA) associated vasculitis is a pauci-immune systemic small vessel vasculitis. ANCA are autoantibodies directed toward an antigen found in neutrophils, either myeloperoxidase (MPO) or proteinase 3 (PR3). ANCA are pathogenic and cause disease by activating neutrophils, which damage blood vessels. ANCA vasculitis may affect various organs and is associated with glomerulonephritis in most patients. The disease can be classified into one of a few phenotypes: microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA, formerly Wegener's granulomatosis), and eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg-Strauss syndrome). However, recent evidence has shown that the ANCA antigen specificity (i.e., MPO- or PR3-ANCA) may be more important in characterizing the disease than the pathologic phenotype (MPA, GPA, or EGPA). ANCA vasculitis is organ- and lifethreatening in many cases, but with early and appropriate therapy, patients can remit. Therapies including corticosteroids, cyclophosphamide, rituximab, and plasmapheresis are effective in inducing a remission in the vast majority of patients. However, relapse is unfortunately common and the existing options for both induction and maintenance therapy are associated with risks for substantial adverse effects. The risks of continued immunosuppression with maintenance therapy must be weighed against the risk of relapsed disease, and there is currently no clear answer regarding the optimal duration of immunotherapy. Although our understanding of this disease has come a long way in a relatively short time, there is still much work to be done in understanding the pathophysiology of disease and identifying better treatment options.