ANCA-associated vasculitis
- Lesion
Antibodies against neutrophil enzymes make neutrophils attack small vessels, mainly in the lungs, airways and kidneys.
What it is
Antineutrophil cytoplasmic antibodies (ANCA) bind proteinase 3 (PR3) or myeloperoxidase (MPO) on cytokine-primed neutrophils, which then degranulate and damage small vessels. The lesions contain little immunoglobulin (pauci-immune). Granulomatosis with polyangiitis (GPA) adds necrotizing granulomas of the airways; microscopic polyangiitis (MPA) has vasculitis without granulomas; eosinophilic GPA (EGPA) adds asthma, eosinophilia and eosinophil-rich granulomas.
Structure
- GPA lung: large nodules with geographic necrosis, palisading histiocytes, giant cells and necrotizing vasculitis; may cavitate.
- Kidney in all three: segmental fibrinoid necrosis of glomerular capillaries with crescents and little or no immunofluorescence staining.
Step by step
- An infection or other inflammatory trigger primes neutrophils, which move PR3 or MPO to their surface.
- ANCA bind these antigens and activate the neutrophils.
- Activated neutrophils release proteases, oxidants and neutrophil extracellular traps onto the endothelium.
- Small vessels undergo fibrinoid necrosis; in GPA granulomas form around necrosis.
- Damage appears in lung, airway and glomeruli; healing leaves scars and crescents.
The three ANCA-associated vasculitides
| Disease | Antibody | Distinctive histology | Typical organs |
|---|---|---|---|
| Granulomatosis with polyangiitis | PR3-ANCA in most | Necrotizing granulomas with geographic necrosis plus vasculitis | Nose and sinuses, lungs, kidneys |
| Microscopic polyangiitis | MPO-ANCA | Fibrinoid necrosis of capillaries and venules, no granulomas | Kidneys, lung capillaries, skin |
| Eosinophilic granulomatosis with polyangiitis | MPO-ANCA in about half | Eosinophil-rich infiltrates and granulomas | Airways (asthma), nerves, heart, skin |
Clinical notes
- Untreated GPA is usually fatal; immunosuppression induces remission in most, and PR3-ANCA levels help follow relapses.
- Lung hemorrhage with acute kidney injury (pulmonary–renal syndrome) suggests ANCA vasculitis or anti-GBM disease.
Test yourself
Think of the answer, then tap the question to see it.
Which three sites form the classic triad of granulomatosis with polyangiitis?
The upper airway (nose, sinuses), the lungs and the kidneys.
Which ANCA vasculitis lacks granulomas?
Microscopic polyangiitis.
Which clinical features suggest eosinophilic GPA?
Asthma, allergic rhinitis, blood eosinophilia, lung infiltrates, neuropathy and often heart involvement.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Granulomatosis with polyangiitis: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2025); Vasculitis| Angiitis | MedlinePlus (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.