Microscopic polyangiitis

• Necrotizing vasculitis commonly involving
• lung, kidneys, and skin
• with pauci-immune glomerulonephritis and palpable purpura.
• Presentation similar to granulomatosis with polyangiitis
• Similar to GPA, but w/o ENT/upper airway involvement & nongranulomatous
• Epidemiology: incidence 4/million/y. ♂ = ♀; avg onset 50–60 y

Clinical manifestations

Constitutional, neuro sx similar to GPA Renal (80–100%): glomerulonephritis Skin lesions (eg, palpable purpura) in 30–60% Pulmonary (25–50%): pulmonary capillary alveolitis, pulmonary fibrosis

Dx studies:

70% ⊕ ANCA (almost all anti-MPO) Biopsy → necrotizing, nongranulomatous inflammation of small vessels, pauci-immune Urine sediment and CXR findings similar to those seen in GPA

Treatment

• as for Treatment of Granulomatosis with polyangiitis
• ↓ relapse rate compared to GPA