Membranoproliferative glomerulonephritis (MPGN) type II (dense deposit disease) is now classified under C3 glomerulopathy. The characteristic ultrastructural finding that distinguishes it from MPGN type I is:

• A Subepithelial immune deposits forming 'humps'
• B Mesangial and subendothelial immune complex deposits
• C Highly electron-dense ribbon-like deposits within the GBM lamina densa ✓
• D Thinning of the GBM with splitting of the lamina densa

Explanation

Dense deposit disease (C3G, formerly MPGN type II) is characterized on electron microscopy by intramembranous, extremely electron-dense, ribbon-like deposits within the GBM lamina densa — giving it the 'dense deposit' appearance. These are not immune complexes but rather C3 breakdown products due to C3 nephritic factor (autoantibody stabilizing C3 convertase). MPGN type I shows mesangial and subendothelial deposits. Subepithelial humps are in post-streptococcal GN. GBM thinning/splitting is in Alport syndrome.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.