Microscopic polyangiitis M31.7

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 20.03.2023

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Angiitis necrotizing non-granulomatous; IMPA; Microscopic polyangiitis; Microscopic polyarteritis; Microscopic polyarteritis nodosa; MPA; necrotizing non-granulomatous angiitis; Periarteritis nodosa cutanea; Polyangiitis microscopic; polyarteritis nodosa; Polyarteritis nodosa microscopic

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Wohlwill, 1923; Arkin, 1930

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Rare, severe, p-ANCA- or c-ANCA positive (60% of patients), necrotizing, non granulomatous (differentiation from granulomatosis with polyangiitis =Wegener's granulomatosis) "small vessel" vasculitis (microscopic) as a (minus) variant of classic polyarteritis nodosa mostly without involvement of medium-sized or large arteries.

MPA is usually accompanied by necrotizing glomerulonephritis and pulmonary capillaritis. Often difficult to differentiate diagnostically from granulomatous vasculitides: Churg-Strauss syndrome/eosinophilia and granulomatosis with polyangiitis/combinationwith sino-nasal symptoms (= Wegener's granulomatosis).

The life-threatening pulmo-renal syndrome requires in most cases intensive care.

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The incidence is 0.6-0.8/100,000 per year.

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Men are more frequently affected than women; the majority of patients are > 50 years old at the beginning of the disease.

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Mostly lower extremities and trunk are affected.

Clinical features
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Prodromal stage with adynamia, subfebrile temperatures, night sweats and weight loss. 50% of patients develop rheumatic complaints (myalgias, arthralgias).

Kidneys:in the further course renal involvement is possible (80%) which can manifest as Rapid Progressive Glomerulonephritis.

Lung: pulmonary capillaritis (25%), hemoptysis, pleurisy, pneumonia.

Heart: cardiovascular system involvement.

Other: gastrointestinal tract and peripheral nervous system (polyneuritis) are possible.

Skin (40%/ the dermatologist is usually involved in this clinical picture only on a consultative basis). Symptoms are nonspecific, clinically difficult to delineate in individual cases because of the high variability of dermatologic symptoms. The symptoms should only be considered in the context of the known clinical diagnosis:

more common is a:

  • Palpable purpura (is in the foreground of the dermatologic symptomatology)

less frequent are:

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Positive (MPO-ANCA) p-ANCA in about 60% of pat. cANCAs may also be present in about 20% of patients.

High inflammatory parameters (ESR; CRP)

Note: pANCAs are not specific for MPA but are also found in other vaculitides.

A pronounced eosinophilia speaks against the disease.

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Inconspicuous epidermis, extensive filling of the corium by dense, perivascularly accentuated infiltration of lymphocytic cells with numerous neutrophilic granulocytes and nuclear dust. Pronounced erythrocyte extravasation. Distinctly swollen vascular endothelia and pronounced fibrin deposits within the vessel walls. Leucocytoclastic vasculitis without immune complex deposits.

Histopathological algorithm of microscopic polyangiitis (polyarteritis) (lowest common denominator:italics, leading symptoms:bold) varies according to Ratzinger et al. 2105
Accentuates around arterioles and small arteries in skin and subcutis
Capillaries omitted or less strongly involved
perivascular and intramural leukocytoclasia
Damage to endothelial cells
Fibrin in/around vessel walls
Perivascular extravasation of erythrocytes
No/mild edema in the papillary dermis
Pathologist. Alterations limited to vascular position, no palisade granulomas
Variable (rather low) eosinophilia
No plasma cells or fibrosclerosis to a variable degree
Reorganization due to lymphocytic vasculitis

Differential diagnosis
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Leukocytoclastic vasculitis: small vessel vasculitis, no positive ANCA serology.

Drug and viral exanthema: no positive ANCA serology

Pyoderma gangraenosum: clinic, localized involvement, ulceration

Granulomatosis with polyangiitis (GPA) - histological evidence of granulomas

Eosinophilic granulomatosis with polyangiitis (EPGPA) - eosinophilic granulomatous infiltrates are the key feature.

In larger collectives with systemic vasculitides, the following breakdowns were shown: 66.7% with GPA, 17.0% with MPA, 16.3% with EGPA(Wójcik K et al. 2019).

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Identical with the therapy of polyarteritis nodosa, see there.

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5-year survival rate: approx. 70%; ANCA and CRP increases indicate a recurrence and a worsened prognosis.

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The dermatological symptoms are extremely variable and not "'diagnosis-specific". Thus, the diagnosis can only be made by evaluating the histopathology in conjunction with the complex overall problem.

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  1. Agard C et al (2003) Microscopic polyangiitis and polyarteritis nodosa: how and when do they start? Arthritis Rheum 49: 709-715
  2. Arkin A (1930) A clinical and pathological study of periarteritis nodosa. A report of five cases, one histologically healed. Am J Pathol 6: 401-410
  3. Frankel SK et al (2002) Vasculitis: Wegener granulomatosis, Churg-Strauss syndrome, microscopic polyangiitis, polyarteritis nodosa, and Takayasu arteritis. Crit Care Clin 18: 855-879
  4. Guillevin L, Lhote F (1995) Polyarteritis nodosa and microscopic polyangiitis. Clin Exp Immunol 101(Suppl1): 22-23.
  5. Harper L, Savage CO (2000) Pathogenesis of ANCA-associated systemic vasculitis. J Pathol 190: 349-359
  6. Hattori N et al (2002) Mortality and morbidity in peripheral neuropathy associated Churg-Strauss syndrome and microscopic polyangiitis. J Rheumatol 29: 1408-1414.
  7. Ratzinger G et al (2015) The vasculitis wheel-an algorithmic approach to cutaneous vasculitides. JDDG 1092-1118
  8. Wagner et al (2002) Microscopic polyangiitis. Act Dermatol 28: 370-373
  9. Wohlwill P (1923) On the form of periarteritis nodosa recognizable only by microscopy. Virchows Arch 246: 377-411
  10. Wójcik K et al. (2019) Clinical characteristics of Polish patients with ANCA-associated
    vasculities-retrospective analysis of POLVAS registry. Clin Rheumatol doi: 10.1007/s10067-019-04538-w.


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Last updated on: 20.03.2023