ANCAassociated

ANCA-associated vasculitis (AAV) is a group of autoimmune diseases defined by inflammation of small- to medium-sized vessels and the presence of anti-neutrophil cytoplasmic antibodies (ANCA). The principal diseases are granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA).

Pathophysiology involves antibodies against neutrophil cytoplasmic antigens, mainly proteinase 3 (PR3) and myeloperoxidase (MPO). ANCA binding activates neutrophils, promoting endothelial injury and necrotizing, pauci-immune vasculitis. The exact triggers are unknown but genetics and environmental factors influence risk.

Clinical features vary but kidney involvement and lung or airway disease are common. Other possibilities include upper airway symptoms, skin lesions, neuropathy, and arthritis. Diagnosis integrates clinical presentation with ANCA testing (PR3-ANCA or MPO-ANCA) and often tissue biopsy showing necrotizing, pauci-immune vasculitis.

Classification includes GPA, MPA, and EGPA; prognosis has improved with targeted immunosuppression, though relapses occur. Monitoring focuses on organ function, infection risk, and treatment-related toxicity rather than ANCA levels alone.

Treatment typically combines high-dose corticosteroids with an immunosuppressant such as rituximab or cyclophosphamide for induction. For limited disease, methotrexate may be used. Plasma exchange is reserved for selected patients with severe kidney involvement or pulmonary hemorrhage. Maintenance therapy (rituximab or azathioprine/methotrexate) follows remission to reduce relapse risk.