EGPA — SCE Rheumatology MCQ

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A 40-year-old woman presents with adult-onset asthma, a blood eosinophil count of 3.2 × 10^9/L, migratory pulmonary infiltrates and mononeuritis multiplex. MPO-ANCA is positive. A biopsy of affected tissue demonstrates necrotising small-vessel vasculitis with prominent extravascular eosinophilic inflammation. What is the most likely diagnosis?

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Correct answer: E — Eosinophilic granulomatosis with polyangiitis (EGPA)

The diagnosis is eosinophilic granulomatosis with polyangiitis. The discriminating features are asthma, marked blood eosinophilia, mononeuritis multiplex and biopsy-proven small-vessel vasculitis with eosinophil-rich extravascular inflammation. Under the 2022 ACR/EULAR classification criteria, eosinophils ≥1 × 10^9/L, obstructive airway disease, eosinophilic inflammation on biopsy and mononeuritis multiplex give 11 points, well above the threshold of 6 once vasculitis and its mimics have been established. MPO-ANCA positivity is compatible with EGPA and is associated particularly with vasculitic manifestations such as neuropathy. Chronic eosinophilic pneumonia and allergic bronchopulmonary aspergillosis do not explain the systemic vasculitic neuropathy. GPA may cause pulmonary disease and mononeuritis multiplex but is not characterised by this asthma–eosinophilia phenotype. Hypereosinophilic syndrome can cause eosinophilic organ injury but is less consistent with this characteristic vasculitic presentation.

Reference: Grayson PC, Ponte C, Suppiah R, et al. 2022 American College of Rheumatology/European Alliance of Associations for Rheumatology Classification Criteria for Eosinophilic Granulomatosis With Polyangiitis. Arthritis & Rheumatology. 2022;74:386–392. https://pubmed.ncbi.nlm.nih.gov/35106968/