Histopathological features of MGCS-related PGNMID and C3 glomerulonephritis. PGNMID (A-C). (A) Light microscopy with periodic acid–Schiff staining (original magnification ×400; scale bar, 50 μm). Membranoproliferative glomerulonephritis with mesangial and endocapillary hypercellularity. (B) Immunofluorescence study showing monotypic IgG glomerular deposits that stained positive with the anti-gamma3 conjugate. Similar staining was observed with the anti-κ conjugate, whereas staining with conjugates specific for α, μ, gamma1, gamma2, and gamma4 heavy chains and λ light-chain conjugate was negative (not depicted). Scale bar, 50 µm. (C) Electron microscopy confirmed the diagnosis of PGNMID with granular nonorganized electron-dense deposits predominant in the subendothelial space (asterisk), suggestive of immune complex–mediated glomerulonephritis (original magnification ×15 000; scale bar, 1 µm). (D-F) MGCS-associated C3 glomerulonephritis. (D) Light microscopy showing a pattern of proliferative endocapillary glomerulonephritis (periodic acid-Schiff staining; original magnification ×400; scale bar, 50 μm). (E) By immunofluorescence, mesangial and glomerular capillary wall deposits stained positively with the anti-C3 FITC-conjugate (original magnification ×200), whereas no staining was observed with conjugates specific for γ, α, and μ heavy chains and with anti-κ and anti-λ conjugates (not depicted). Scale bar, 50 µm. (F) Electron microscopy demonstrated the presence of voluminous subepithelial electron-dense deposits (humps, asterisk) and interrupted intramembranous dense deposits (arrows) (original magnification ×15 000; scale bar, 1 µm)