A 68-year-old man presents with rapidly progressive glomerulonephritis, reaching a creatinine of 6 mg/dL over three weeks. Biopsy shows crescents in more than 50 percent of glomeruli. Immunofluorescence shows little or no staining for immunoglobulin or complement, and serum MPO-ANCA is positive. How is this entity classified?
- A Type I RPGN, anti-GBM mediated
- B Type III RPGN, pauci-immune ✓
- C Type II RPGN, immune complex mediated
- D Type IV RPGN, double positive for anti-GBM and ANCA
Correct answer: B. Type III RPGN, pauci-immune
Explanation
Pauci-immune crescentic glomerulonephritis associated with ANCA, seen in granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis, constitutes type III RPGN and is the most common form in older adults. Type I shows linear IgG along the GBM, and type II shows granular immune complex deposits as in lupus or post-infectious GN. Absent immunoglobulin staining rules out both.
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.