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Kidney non-tumor

Associated with systemic conditions

Microscopic polyangiitis

Reviewers: Nikhil Sangle, M.D. (see Reviewers page)
Revised: 12 December 2012, last major update December 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.


● Systemic, pauci-immune, small-vessel necrotizing vasculitis associated with anti-neutrophil cytoplasmic antibodies (ANCA), often targeting myeloperoxidase (MPO), but without immune complex deposition or granulomas
● A type of pauci-immune vasculitis (necrotizing small-vessel vasculitis with no immune complex deposition by EM or immunofluorescence)
● Previously considered a type of polyarteritis nodosa (eMedicine)

Clinical features

● Affects 1 per 100,000; any age but more common at age 50+ years
● 90% have renal involvement; lungs usually affected (may simulate Goodpasture’s syndrome)
● Also skin, ear, nose, throat, musculoskeletal, nervous system, GI
● Symptoms: hematuria, proteinuria, hemoptysis, palpable purpura, abdominal pain, myalgias, arthralgias, mild hypertension
● Birmingham Vasculitis Activity Score (BVAS, online calculator): useful for determining disease activity and outcome (Clin Rheumatol 2011;30:1499)
● Survival of 60-80% at 10 years, death mainly in first months after diagnosis (Rheumatology (Oxford) 2011;50:1414)
● Laboratory: PR3-ANCA (40%), MPO-ANCA (50%), negative (10%)
● Treatment: IV corticosteroids, immunosuppressants, transplant (Clin J Am Soc Nephrol 2010;5:445, Am J Nephrol 2011;33:185)

Case reports

● 59 year old man with myeloperoxidase-ANCA negative microscopic polyangiitis with pulmonary hemorrhage and IgA nephropathy (Case Rep Dermatol 2011;3:22)

Micro description

● Glomerulonephritis (focal and segmental to severe diffuse and crescentic)
● Arterial lesions usually all at same stage
● Usually tubulointerstitial infiltrate
● Sausage shaped microaneurysms of interlobular arteries
● No granulomas or asthma (Hum Pathol 1998;29:223)

Micro images

Microscopic polyangiitis: A-acute focal segmental necrotizing glomerulonephritis; B-interstitial inflammation and arteritis

Patient with ANCA-associated microscopic polyangiitis and focal necrotizing glomerulonephritis

Glomerulus shows segmental fibrinoid necrosis with adjacent small cellular crescent; PAS shows focal dissolution of Bowman's capsule basement membrane (arrows); .glomerular basement membranes and mesangial matrix have been destroyed near the fibrinoid necrosis; note the periglomerular tubulointerstitial inflammation and edema

Mild mesangial cellular proliferation and expansion; mesangial and diffuse IgA deposits were observed but crescents were absent

Red blood cell cast (urine)

Virtual slides

Microscopic polyangiitis (polyarteritis)


● No deposits

Electron microscopy description

● No deposits

Differential diagnosis

● Other pauci-immune glomerulonephritis including Wegener’s granulomatosis (necrotizing granulomas), Churg-Strauss syndrome / allergic granulomatosis and angiitis (eosiniophilia, asthma, granulomas)

End of Kidney non-tumor > Associated with systemic conditions > Microscopic polyangiitis

Ref Updated: 7/31/12

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