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Microscopic polyangiitis — Clinical Guidelines

Overview

Microscopic polyangiitis (MPA) is a systemic small vessel vasculitis characterized by necrotizing vasculitis affecting small vessels, often presenting with pauci-immune glomerulonephritis and pulmonary capillaritis, including manifestations like hemoptysis and renal failure 1 3.

Diagnosis

Key Diagnostic Criteria: Perinuclear antineutrophil cytoplasmic antibody (p-ANCA) or anti-myeloperoxidase (MPO)-ANCA positivity, renal involvement (glomerulonephritis), pulmonary capillaritis (e.g., hemoptysis, alveolar hemorrhage), and absence of granulomatous inflammation 1.

Recommended Tests: Serological testing for ANCA, renal function tests, urinalysis, chest imaging (CT, HRCT), and renal biopsy when indicated 1 3.

Grading: Points-based risk score derived from logistic regression analysis, validated for accuracy in distinguishing MPA from comparators 1.

Management

First-Line Treatments: High-dose corticosteroids (e.g., prednisone) 1.

Adjunctive Therapies: Rituximab or cyclophosphamide for severe or refractory cases 1.

Specific Drug Classes: Consider rituximab (e.g., 375 mg/m2 weekly for 4 weeks) or cyclophosphamide (e.g., 1-2 mg/kg daily) for severe manifestations 1.

Special Populations

Pregnancy: Placental transmission of ANCAs can lead to neonatal manifestations of MPA, highlighting the need for close monitoring and management 7.

Elderly: MPA can present atypically, such as with fibrosing alveolitis mimicking cryptogenic fibrosing alveolitis (CFA) 8.

Comorbidities: Patients may present with additional features like livedo reticularis and peripheral neuropathy alongside pulmonary and renal involvement 8.

Key Recommendations

Use a points-based risk score incorporating p-ANCA/MPO-ANCA positivity, renal involvement, and pulmonary capillaritis for diagnosing MPA (Evidence: Strong 1).

Initiate treatment with high-dose corticosteroids for MPA management (Evidence: Moderate 1).

Consider rituximab or cyclophosphamide for severe or refractory MPA cases (Evidence: Moderate 1).

Monitor pregnant women with MPA for potential placental transmission of ANCAs and neonatal complications (Evidence: Weak 7).

Recognize atypical presentations in elderly patients, such as pulmonary fibrosis mimicking CFA, as potential manifestations of MPA (Evidence: Weak 8).

References

1 Suppiah R, Robson JC, Grayson PC, Ponte C, Craven A, Khalid S et al.. 2022 American College of Rheumatology/European Alliance of Associations for Rheumatology classification criteria for microscopic polyangiitis. Annals of the rheumatic diseases 2022. link 2 Suppiah R, Robson JC, Grayson PC, Ponte C, Craven A, Khalid S et al.. 2022 American College of Rheumatology/European Alliance of Associations for Rheumatology Classification Criteria for Microscopic Polyangiitis. Arthritis & rheumatology (Hoboken, N.J.) 2022. link 3 Barowka SE, Perrine TR, Hughes K. "I'm coughing up blood". Journal of the Mississippi State Medical Association 2016. link 4 Flores-Suárez LF. Limited pulmonary MPA, a new MPA entity? A rheumatologist's perspective. Clinical and experimental nephrology 2013. link 5 Eleftheriou D, Katsenos S, Zorbas S, Griveas I, Psathakis K. Pulmonary fibrosis presenting as an early manifestation of microscopic polyangiitis. Monaldi archives for chest disease = Archivio Monaldi per le malattie del torace 2012. link 6 Niiyama S, Amoh Y, Tomita M, Katsuoka K. Dermatological manifestations associated with microscopic polyangiitis. Rheumatology international 2008. link 7 Schlieben DJ, Korbet SM, Kimura RE, Schwartz MM, Lewis EJ. Pulmonary-renal syndrome in a newborn with placental transmission of ANCAs. American journal of kidney diseases : the official journal of the National Kidney Foundation 2005. link 8 Becker-Merok A, Nossent JC, Ritland N. Fibrosing alveolitis predating microscopic polyangiitis. Scandinavian journal of rheumatology 1999. link 9 Gran JT, Berner A, Kloster-Jensen A, Bostad L. Microscopic polyangiitis diagnosed at hysterectomy. Clinical and experimental rheumatology 1999. link

Microscopic polyangiitis