DDD Intramembranous Ribbon C3NeF — ESENeph MCQ

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HardGlomerulonephritisDDD Intramembranous Ribbon C3NeFESENeph

A 44-year-old man with membranoproliferative glomerulonephritis (MPGN) pattern on biopsy has C3-only deposits on immunofluorescence with electron-dense intramembranous ribbon-like deposits on electron microscopy. C3 is low, C4 is normal. C3 nephritic factor (C3NeF) is positive. What is the specific diagnosis within C3 glomerulopathy?

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Correct answer: D — Dense deposit disease (DDD)

Dense deposit disease (DDD), formerly MPGN type II, is characterised by pathognomonic continuous, ribbon-like, electron-dense deposits within the glomerular basement membrane on EM. It is classified within C3 glomerulopathy (C3G) based on C3-dominant/only immunofluorescence staining. C3NeF is an autoantibody (IgG) that stabilises the C3 convertase (C3bBb), preventing its inactivation by factor H, leading to persistent alternative complement pathway activation and C3 consumption. This explains the low C3 with normal C4. C3 glomerulonephritis (C3GN) has similar IF but different EM findings (subendothelial/mesangial deposits rather than intramembranous ribbons). Treatment options include MMF, eculizumab, and investigational C3 inhibitors.

Reference: Sethi & Fervenza 2012 – C3 Glomerulopathy; Pickering et al 2013 – C3G Consensus