A 7-year-old boy presents with cola-colored urine, periorbital edema, and hypertension 2 weeks after a throat infection. Renal biopsy shows diffuse hypercellularity with neutrophil infiltration and 'humps' on electron microscopy. Complement C3 is low. What is the underlying immunopathologic mechanism?
- A Anti-GBM antibody-mediated damage (Goodpasture mechanism)
- B ANCA-mediated pauci-immune inflammation
- C Immune complex deposition activating the classical complement pathway ✓
- D T-cell mediated podocyte injury
Correct answer: C. Immune complex deposition activating the classical complement pathway
Explanation
Post-streptococcal glomerulonephritis is caused by immune complex deposition (streptococcal antigen-antibody complexes) in the subepithelial space, forming the characteristic 'humps' on electron microscopy. These complexes activate the classical complement pathway, consuming C3 and C4, causing a nephritis picture. The latent period of 1–3 weeks after pharyngitis corresponds to the time for antibody production.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.