Membranoproliferative glomerulonephritis (MPGN) type I shows a characteristic 'tram-track' or double contour of the GBM on silver stain. This appearance results from:
- A Mesangial cell interposition between the GBM and endothelium with new matrix deposition ✓
- B Subepithelial immune complex deposits lifting the GBM
- C Splitting of the lamina densa by dense deposits within the GBM
- D Podocyte proliferation forming crescents compressing capillaries
Correct answer: A. Mesangial cell interposition between the GBM and endothelium with new matrix deposition
Explanation
In MPGN type I, mesangial cells extend into peripheral capillary loops (mesangial interposition) between the endothelium and the GBM. This, together with new basement membrane material laid down by the interposing cells, creates the characteristic double contour or 'tram-track' appearance on PAS and silver stains. MPGN type II (dense deposit disease) shows intramembranous electron-dense deposits due to C3 nephritic factor.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.