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ANCA-associated vasculitis — ABIM Board MCQ

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HardRheumatology/Allergy/ImmunologyANCA-associated vasculitisABIM Board

A 66-year-old man has chronic sinusitis, hemoptysis, palpable purpura, creatinine 2.3 mg/dL, dysmorphic erythrocytes, and red-cell casts. CT shows cavitary pulmonary nodules and PR3-ANCA is positive. He is stable without diffuse alveolar hemorrhage. Which test best confirms the diagnosis and guides prognosis?

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Correct answer: C — Obtain a kidney biopsy while preparing organ-threatening vasculitis treatment

The best answer is “Obtain a kidney biopsy while preparing organ-threatening vasculitis treatment”. This is a pulmonary-renal syndrome strongly suggesting granulomatosis with polyangiitis. Kidney biopsy can demonstrate pauci-immune necrotizing crescentic glomerulonephritis, quantify chronic damage, and exclude mimics. A strongly compatible ANCA result supports but does not replace tissue when safe and informative. Treatment of organ-threatening disease should be prepared promptly and should not be withheld if biopsy logistics create a dangerous delay.

Reference: ACR/Vasculitis Foundation guideline for ANCA-associated vasculitis: https://pmc.ncbi.nlm.nih.gov/articles/PMC12344527/