ANCA Vasculitis Classification and Management

Disease Classification

The American College of Rheumatology recommends classifying ANCA-associated vasculitis (AAV) using the Chapel Hill Consensus Conference (CHCC) definitions combined with ACR criteria, which categorize disease by vessel size, clinical phenotype, and ANCA serotype 1, 2
Granulomatosis with Polyangiitis (GPA) is characterized by necrotizing granulomatous inflammation plus vasculitis, predominantly affecting small to medium vessels, and is most commonly associated with PR3-ANCA and cytoplasmic ANCA (C-ANCA) 1, 2, 3
Microscopic Polyangiitis (MPA) is characterized by vasculitis without granulomatous inflammation, affecting small vessels, and is most commonly associated with MPO-ANCA and perinuclear ANCA (P-ANCA) 2, 3
Eosinophilic Granulomatosis with Polyangiitis (EGPA) is characterized by eosinophilic tissue infiltration plus vasculitis, affecting small to medium vessels, and only 40% of patients are ANCA-positive 2, 3

The European Vasculitis Study Group recommends categorizing AAV by disease severity to guide treatment decisions, with categories including Localized, Early Systemic, Generalized, Severe, and Refractory 4

High-quality antigen-specific immunoassays for MPO-ANCA and PR3-ANCA are the preferred screening method, with approximately 90% of patients with small-vessel vasculitis having detectable ANCA 5
Biopsy showing necrotizing vasculitis, granulomatous inflammation, or pauci-immune glomerulonephritis is the gold standard for diagnosis, but treatment should not be delayed waiting for biopsy results in rapidly deteriorating patients 5, 6

Rituximab is conditionally recommended over cyclophosphamide for remission induction in severe/generalized disease (GPA/MPA), combined with reduced-dose glucocorticoid regimen to minimize toxicity 1, 2, 7
Mepolizumab is recommended for non-severe EGPA 1, 2
Pneumocystis jirovecii prophylaxis is mandatory in patients receiving rituximab or high-dose immunosuppression 7, 9

Delaying treatment in ANCA-positive patients with compatible clinical presentation while awaiting biopsy, particularly in rapidly deteriorating patients, should be avoided 5
Using ANCA subtype alone for classification, as up to 30% of MPA patients are PR3-ANCA positive without typical GPA features, should be avoided 8
Omitting Pneumocystis jirovecii prophylaxis in patients receiving rituximab or high-dose immunosuppression should be avoided 7, 9