Kidney biopsy from a 35-year-old with nephrotic syndrome shows diffuse mesangial proliferation, subendothelial deposits on electron microscopy, and C3-dominant granular deposits on immunofluorescence with 'mesangial fingerprint' pattern. No ANA, ANCA, or anti-GBM antibodies. C3 is low; C4 is normal. Serum shows a C3 nephritic factor. This pattern is most consistent with:
- A Immune complex-mediated MPGN (Type I MPGN)
- B Dense deposit disease (C3 glomerulopathy, DDD subtype)
- C C3 glomerulopathy (C3 glomerulonephritis subtype) ✓
- D Fibrillary glomerulonephritis
Explanation
C3 glomerulonephritis (C3GN) is characterized by C3-dominant glomerular deposits (C3 ≥2 orders of magnitude more intense than any Ig on IF) with alternate pathway dysregulation evidenced by low C3, normal C4, and C3 nephritic factor (C3NeF), which stabilizes the alternate pathway C3 convertase. C3GN is one subtype of C3 glomerulopathy; the other is dense deposit disease (DDD). In DDD, electron microscopy shows intramembranous dense deposits forming dense ribbons, whereas C3GN shows mesangial and subendothelial deposits without the characteristic dense osmiophilic deposits. The 'mesangial fingerprint' in C3GN distinguishes it from DDD.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.