Track

Basic Science

Abstract

Eosinophilic granulomatosis with polyangiitis (EGPA), is a rare, multisystem inflammatory disease associated with asthma, peripheral eosinophilia, rhinosinusitis and neuropathy. About 40% of cases are antineutrophilic cytoplasmic antibody (ANCA) positive. Biopsies show heterogenous inflammatory patterns including tissue eosinophilia, interstitial granulomatous inflammation, leukocytoclastic vasculitis (LCV), granulomatous vasculitis and an eosinophilic vasculopathy. We aimed to explore the histopathology of EGPA and its significance pertaining to clinical course. We identified 12 patients (7F, 5M, age = 16-66) who had biopsy proven EGPA from our 2016-2024 database. Histories included allergic rhinitis, asthma and or peripheral blood eosinophilia. ANCA status of 9 patients was known. Skin findings included palpable purpura, papules, nodules, ulcers and livedo. In each case the biopsy was confirmatory of EGPA. Six cases showed a predominant neutrophil-rich necrotizing LCV in association with microvascular C5b-9 where a diagnosis of ANCA+ EGPA was favored. Five of these patients were ANCA+. In biopsies showing interstitial and palisading granulomatous inflammation (+/- necrobiotic change), granulomatous and lymphocytic vasculitis and tissue eosinophilia a diagnosis of ANCA- EGPA was suggested; the patients were established to be ANCA-. Microvascular eosinophil granule containing thrombi suggested a concurrent underlying procoagulant state which was confirmed clinically as revealed by embolic events and elevated D dimers. Three ANCA- cases showed in vivo neutrophilic extracellular traps (NET). Cutaneous histologic EGPA variants predicts the clinical phenotype. Patients with ANCA+ EGPA have neutrophil-rich cutaneous and extravascular vasculitis. Microvascular thrombosis defines a thrombophilic variant while in ANCA- EGPA NETosis, granulomatous vasculitis and eosinophilia are integral to multiorgan dysfunction.