PMC7772466_01
Light microscopy findings in patient #1: first biopsy showed membranoproliferative glomerulonephritis with focal mesangial nodules, and endocapillary mononuclear and polymorphonuclear leukocytes (A, PAS; B, PAS; C, Masson Trichrome). The repeat biopsy showed a remarkable reduction of the membranoproliferative lesions with disappearance of the capillary leukocyte infiltration and persistent mesangial expansion (D, PAS; E, PAS; F, Masson Trichrome).
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F1
Light microscopy showed membranoproliferative glomerulonephritis with nodular mesangial expansion, and infiltrating mononuclear and polymorphonuclear leukocytes (Figures 1A-C).
Immunofluorescence findings in patient #1: the first biopsy showed bright positivity (3+) for C3 (A) and k-light chain (B) involving the glomerular capillary walls and the mesangium, while it resulted negative for lambda-light chain (C). The repeat biopsy showed substantial negative staining for C3 (D) and k and lambda -light chain (E, F).
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F2
Immunofluorescence showed positive staining for C3 (3+) and k-light chain (3+) involving glomerular capillary walls and the mesangium, with negative staining for lambda-light chain and for heavy chain, performed both on frozen material (Figures 2A-C) and on formalin-fixed paraffin embedded tissue after protease digestion (not shown).
Electron microscopy findings in patient #1: the first biopsy showed subendothelial (A, original magnification, x3900) and mesangial (B, original magnification, x2950) electron dense deposits, while no deposits were seen along the tubular basement membranes (C, original magnification, x2950). The repeat biopsy showed complete disappearance of the subendothelial and mesangial deposits. (D, original magnification, x2200; E, original magnification, x6610; F, original magnification, x8900).
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F3
Ultrastructural evaluation highlighted subendothelial and mesangial electron dense deposits, with no deposits along the tubular basement membranes (Figures 3A-C).
PMC7772466_02
Light microscopy findings in patient #2: the first biopsy showed membranoproliferative glomerulonephritis with nodular mesangial expansion, and infiltrating mononuclear and polymorphonuclear leukocytes (A, PAS; B, Masson Trichrome; C, wide deposits along the glomerular basement membranes appear pink on AFOG staining). The repeat biopsy showed a remarkable reduction of the membranoproliferative lesions with disappearance of the capillary leukocyte infiltration and persistent mesangial expansion (D, PAS; E, Masson Trichrome; F, small mesangial deposits on AFOG staining).
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F4
Light microscopy showed membranoproliferative glomerulonephritis with nodular mesangial expansion, occasional protein thrombi and numerous endocapillary infiltrating mononuclear and polymorphonuclear leukocytes (Figures 4A-C). Renal biopsy was repeated after 12 months and showed a significant reduction of the membranoproliferative lesions, disappearance of the capillary leukocyte infiltration and of the protein thrombi, and persistent but less evident nodular mesangial expansion (Figures 4D-F).
Immunofluorescence findings in patient #2: the first biopsy showed positive, coarsely granular, staining for C3 (3+), IgG (2+/3+, A), C1q (1+) and lambda-light chain (3+, B) involving glomerular capillary walls and, occasionally, the mesangium, while it resulted negative for k-light chain (C). The repeat biopsy showed less evident glomerular capillary wall and mesangial staining for C3 (2+, D) with complete disappearance of lambda-light chain deposition (E).
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F5
Immunofluorescence demonstrated positive, coarsely granular, staining for C3 (3+), IgG (2+), C1q (1+) and lambda-light chain (3+) involving glomerular capillary walls and, occasionally, the mesangium, with negative staining for k-light chain (Figures 5A-C). On immunofluorescence there was less evident glomerular capillary wall and mesangial staining for C3 (2+) with complete disappearance of lambda-light chain deposition (Figures 5D,E).
Ultrastructural findings in patient #2: the first biopsy showed large subendothelial, intramembranous, and mesangial electron dense deposits composed of microtubules (27-30 nm) with hollow centers, organized in parallel arrays (A, original magnification, x39000; B, original magnification x15500; C, original magnification, x15500). The repeat biopsy showed the nearly complete disappearance of the subendothelial, intramembranous and mesangial electron dense, microtubular deposits (D, original magnification, x1650; E, original magnification, x3900; F, original magnification, x11500: small occasional residual deposits).
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F6
Ultrastructural evaluation showed large subendothelial, intramembranous, and mesangial electron dense deposits composed of microtubules (27-30 nm) with hollow centers, organized in parallel arrays (Figures 6A-C) consistent with immunotactoid glomerulonephritis. Electron microscopy demonstrated nearly complete disappearance of the subendothelial, intramembranous and mesangial electron dense, microtubular deposits (Figures 6D-F).