ANCA interpretation — SCE Rheumatology MCQ

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ModerateMusculoskeletal InvestigationsANCA interpretationSCE Rheumatology

A 60-year-old man has rapidly progressive glomerulonephritis and pulmonary haemorrhage. ANCA testing shows MPO-ANCA positivity. Renal biopsy demonstrates pauci-immune necrotising crescentic glomerulonephritis without granulomas. What is the most likely diagnosis?

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Correct answer: B — Microscopic polyangiitis

Explanation lettering: D = shown as A · A = shown as C · E = shown as D · C = shown as E

Microscopic polyangiitis is best because MPO-ANCA, pulmonary capillaritis and pauci-immune crescentic GN without granulomatous ENT disease support microscopic polyangiitis. A is less suitable because SLE nephritis is immune-complex mediated with full-house staining; C is less suitable because anti-GBM disease would have anti-GBM antibodies and linear IgG on biopsy; D is less suitable because IgA vasculitis has IgA deposition; E is less suitable because GPA is more associated with PR3-ANCA and granulomatous ENT/lung disease. Clinical pearl: renal biopsy pattern is often more decisive than antibody positivity alone.

Reference: EULAR AAV recommendations 2022; BSR ANCA-associated vasculitis recommendations 2025