C3 glomerulopathy is a broad term encompassing-
- dense deposit disease (DDD), former MPGN type II
- C3 glomerulonephritis
- CFHR5 nephropathy
C3 glomerulopathy cases have low serum C3 levels (hypocomplementemia).
C3 glomerulonephritis comprises examples of MPGN types I and III, in which immunofluorescence reveals predominant C3 deposits.
Both C3GN and DDD have similar Light microscopy findings.
- Hypercellular, Lobulated glomeruli
- Duplicated basement membranes in capillary walls
- ↑↑ Mesangial matrix
Immunofluorescence – Similar in both C3GN and DDD
Bright mesangial and glomerular capillary wall staining for C3. Immunoglobulins (IgG) are absent.
Electron Microscopy – (different electron dense pattern)
Mesangial and subendothelial electron-dense “waxy” deposits of C3.
lamina densa and subendothelial space of the GBM are transformed into an irregular, ribbonlike, and extremely electron-dense structure.
The following is commonly associated with upregulated alternative complement pathway –
- Autoantibodies that stabilize C3 convertase -C3NeF (C3 Nephritic factors)
- Mutation in complement regulatory protein genes
- Factor H
- Factor I
Acquired or hereditary abnormality of the alternative pathway of complement system→ Unregulated activation of Alternative Pathway (antibody-independent pathway) → Increased Inflammation and inflammatory mediators → Glomerular Injury → ESRD
DDD cases present at younger ages. And the onset of disease in C3GN is generally around older age.
Common in both C3GN and DDD
- Renal Insufficiency
Most commonly associated with DDD
- Ocular drusen (yellow deposits in the retina)
- Acquired Partial lipodystrophy
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