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ANCA vasculitis renal involvement — SCE Rheumatology MCQ

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ModerateVasculitisANCA vasculitis renal involvementSCE Rheumatology

A 61-year-old man presents with weight loss, chronic bloody nasal discharge and palpable purpura. His serum creatinine has increased from 85 micromol/L three months ago to 210 micromol/L. Urine microscopy shows dysmorphic erythrocytes and red-cell casts, and PR3-ANCA is positive. His blood pressure, platelet count and coagulation screen are normal. Which investigation would best confirm the cause of his renal impairment and provide renal prognostic information?

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Correct answer: E — Percutaneous renal biopsy

The correct answer is E. The combination of upper-airway disease, purpura, PR3-ANCA positivity and rapidly deteriorating renal function with a glomerular urinary sediment strongly suggests granulomatosis with polyangiitis causing ANCA-associated glomerulonephritis. Renal biopsy can demonstrate pauci-immune necrotising crescentic glomerulonephritis, exclude alternative renal pathology and provide prognostic information from the proportions of normal, crescentic and sclerosed glomeruli. Skin biopsy may confirm small-vessel vasculitis but cannot characterise the renal lesion; nasal biopsy has lower diagnostic yield. Sinus CT assesses structural ENT disease rather than renal involvement. Repeating PR3-ANCA does not establish renal histology or activity. Biopsy should be obtained promptly, but treatment of organ-threatening disease should not be delayed if biopsy is unsafe or unavailable.

Reference: Hellmich B et al. EULAR recommendations for the management of ANCA-associated vasculitis: 2022 update, diagnostic recommendation on biopsy and ANCA testing. Ann Rheum Dis. 2024;83:30-47. https://pubmed.ncbi.nlm.nih.gov/36927642/