Abstract
Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) represents a group of small vessel vasculitides characterized by granulomatous and neutrophilic tissue inflammation, often associated with the production of antibodies that target neutrophil antigens. The two major antigens targeted by ANCAs are leukocyte proteinase 3 (PR3) and myeloperoxidase (MPO). AAV can be classified into 3 categories based on patterns of clinical involvement: namely, granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic GPA (EGPA). Clinically, AAV involves many organ systems including the lungs, kidneys, skin, and nervous system. The prognosis of AAV has improved dramatically due to advances in the understanding of its pathogenesis and treatment modalities. This review will highlight some of the recent updates in our understanding of the pathogenesis, clinical manifestations, and treatment options in patients with AAV focusing on kidney involvement.
Highlights
The pathogenesis of associated vasculitis (AAV) is complex and includes genetic, environmental, and infectious factors
The hallmark of AAV is the presence of necrotizing inflammation and fibrinoid necrosis in the walls of small and medium-sized vessels, which may be accompanied by necrotizing granulomas in granulomatosis with polyangiitis (GPA), or eosinophilic infiltrates in eosinophilic GPA (EGPA)
A retrospective study of 114 patients with severe associated glomerulonephritis (AAGN) that were treated with plasma exchange (PLEX), glucocorticoids, and CYC did not demonstrate any improvement in survival, renal recovery, or relapses in patients receiving intravenous methylprednisolone (IVMP) compared to patients who did not
Summary
The pathogenesis of AAV is complex and includes genetic, environmental, and infectious factors. The production of antibodies targeting self-antigens and maintenance of autoreactive B-cells highlight the key role of loss of tolerance in AAV (Figure 1). How this occurs in AAV is incompletely understood, but multiple pathways have been proposed. Patients with AAV have lower levels of and/or dysfunctional B and T regulatory lymphocytes (Breg and Treg, respectively) [44,45,46,47] Other stimuli, such as active infection and environmental exposures, may lead to increased expression and release of MPO and PR3 as part of neutrophil extracellular traps (NETs), further exposing these antigens to antigen presenting cells [25,36,48]. TheC5a receptor blocker avacopan was efficacious in management of AAV (discussed later) [72,73]
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