A 25-year-old man presents with recurrent epistaxis, hemoptysis, and hematuria. CT shows multiple pulmonary cavitary nodules. c-ANCA (PR3-ANCA) is positive. Renal biopsy shows pauci-immune necrotizing glomerulonephritis with crescent formation. Which of the following is the definitive renal biopsy finding that distinguishes this condition from immune complex-mediated glomerulonephritis?

• A Subepithelial immune complex deposits on electron microscopy
• B Linear IgG deposition along the glomerular basement membrane
• C Mesangial IgA-dominant immune deposits
• D Markedly reduced or absent immune complex and complement deposition (pauci-immune) ✓

Explanation

The clinical picture is granulomatosis with polyangiitis (Wegener), a PR3-ANCA-associated small-vessel vasculitis. The renal hallmark is pauci-immune necrotizing crescentic glomerulonephritis, defined by little or no immunoglobulin or complement deposition on immunofluorescence, in contrast to immune complex-mediated or anti-GBM diseases. Option A is post-infectious GN. Option B is Goodpasture syndrome. Option C is IgA nephropathy. The pauci-immune pattern is the key discriminator and a favorite exam fact.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.