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ANCA renal disease — SCE Rheumatology MCQ

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ModerateMusculoskeletal investigationsANCA renal diseaseSCE Rheumatology

A 56-year-old man presents with chronic sinus symptoms, small-volume haemoptysis and palpable purpura. Urinalysis shows blood 3+ and protein 2+, and urine microscopy demonstrates dysmorphic erythrocytes and red-cell casts. His serum creatinine has risen from 88 to 245 micromol/L over 2 weeks. PR3-ANCA is positive. Which single investigation should be prioritised to secure the diagnosis and provide prognostic information about the organ-threatening process, provided that arranging it does not delay urgent treatment?

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Correct answer: B — Renal biopsy

The correct answer is B, renal biopsy. The upper-airway, pulmonary, cutaneous and rapidly progressive glomerular manifestations with PR3-ANCA strongly suggest granulomatosis with polyangiitis. Renal biopsy can demonstrate pauci-immune necrotising crescentic glomerulonephritis, exclude important mimics and provide prognostic information from the proportions of normal, crescentic and chronically damaged glomeruli. Urgent induction treatment must not be delayed if biopsy cannot be performed promptly. Nasal biopsy has limited sensitivity, while skin biopsy may show small-vessel vasculitis without defining the renal lesion. Bronchoscopy is useful when diffuse alveolar haemorrhage or pulmonary infection requires clarification, but does not assess the cause or prognosis of the kidney injury. Sinus CT defines structural ENT disease but provides no tissue diagnosis.

Reference: Hellmich B, Sanchez-Alamo B, Schirmer JH, et al. EULAR recommendations for the management of ANCA-associated vasculitis: 2022 update, recommendation on biopsy and ANCA testing. Ann Rheum Dis. Published online 2023;83:30–47. https://pubmed.ncbi.nlm.nih.gov/36927642/