An 8-year-old child develops nephritic syndrome 2 weeks after a streptococcal throat infection. Renal biopsy shows subepithelial 'humps' on electron microscopy. The key pathogenic mechanism is:
- A Circulating immune complex deposition in subepithelial space ✓
- B In situ immune complex formation with planted antigens
- C Anti-glomerular basement membrane antibody deposition
- D Complement alternative pathway dysregulation
Correct answer: A. Circulating immune complex deposition in subepithelial space
Explanation
Post-streptococcal glomerulonephritis is a classic Type III hypersensitivity reaction where circulating antigen-antibody complexes deposit subepithelially, producing the characteristic 'humps' on electron microscopy. Anti-GBM is Goodpasture syndrome. A3 glomerulopathy involves complement dysregulation. In situ formation is seen in membranous nephropathy (PLA2R antigen).
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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