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Microscopic polyangiitis (microscopic polyarteritis)
J C Jennette1, D B Thomas, R J Falk
1Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill 27599-7525, USA.
Abstract:
Microscopic polyangiitis ("microscopic polyarteritis") is a form of necrotizing small vessel vasculitis that most often affects venules, capillaries, arterioles, and small arteries, although it occasionally involves medium-sized arteries. Microscopic polyangiitis is a more appropriate name than microscopic polyarteritis because some patients have no evidence for arterial involvement. The absence or paucity of immunoglobulin localization in vessel walls distinguishes microscopic polyangiitis from immune complex mediated small vessel vasculitis, such as Henoch-Schonlein purpura and cryoglobulinemic vasculitis. Clinical, epidemiological, and pathologic differences warrant the separation of microscopic polyangiitis from polyarteritis nodosa on the basis of involvement of capillaries and venules by the former but not the latter. Pauci-immune necrotizing and crescentic glomerulonephritis, and hemorrhagic pulmonary capillaritis are common in patients with microscopic polyangiitis. Microscopic polyangiitis is the most common cause for pulmonary-renal vasculitic syndrome. The vasculitis in patients with microscopic polyangiitis is pathologically indistinguishable from the vasculitis of Wegener's granulomatosis and Churg-Strauss syndrome. Granulomatous inflammation distinguishes Wegener's granulomatosis from microscopic polyangiitis. Asthma and eosinophilia distinguish Churg-Strauss syndrome from microscopic polyangiitis. Microscopic polyangiitis, Wegener's granulomatosis, and Churg-Strauss syndrome are all associated with circulating antineutrophil cytoplasmic autoantibodies.
Insights
Microscopic polyangiitis is a necrotizing small vessel vasculitis. It is distinguished from other vasculitides by pauci-immune glomerulonephritis and pulmonary capillaritis, often without immune deposits.
Area of Science:
- Rheumatology
- Nephrology
- Pulmonology
Background:
- Microscopic polyangiitis (MPA) is a necrotizing small vessel vasculitis.
- MPA primarily affects venules, capillaries, arterioles, and small arteries.
- It is differentiated from immune complex vasculitis by the absence of significant immunoglobulin deposition.
Purpose of the Study:
- To clarify the distinct pathological and clinical features of microscopic polyangiitis.
- To differentiate MPA from other small and medium-sized vessel vasculitides.
- To highlight MPA's common renal and pulmonary manifestations.
Main Methods:
- Pathological examination of vessel walls, focusing on inflammation and immune deposits.
- Clinical assessment of patient symptoms, including renal and pulmonary involvement.
- Serological testing for antineutrophil cytoplasmic autoantibodies (ANCAs).
Main Results:
- MPA is characterized by pauci-immune necrotizing and crescentic glomerulonephritis.
- Hemorrhagic pulmonary capillaritis is a frequent finding in MPA.
- MPA shares pathological features with Wegener's granulomatosis and Churg-Strauss syndrome but lacks granulomatous inflammation or eosinophilia, respectively.
- Circulating ANCAs are associated with MPA, Wegener's granulomatosis, and Churg-Strauss syndrome.
Conclusions:
- Microscopic polyangiitis is a distinct vasculitic entity characterized by small vessel necrotizing inflammation.
- Pauci-immune glomerulonephritis and pulmonary capillaritis are hallmarks of MPA.
- Distinguishing MPA from other ANCA-associated vasculitides relies on the absence of granulomatous inflammation and eosinophilia.