PMC9659563_01
Pathological features of light microscopy and immunohistochemistry. (A,B) Small amounts of erythrophilin were deposited under epithelial cells, and vacuolar degeneration of renal tubular epithelial cells (Masson staining, 200 x and 400x, respectively). (C) Deposition of eosinophilic homogeneous unstructured material in the mesangial region, capillary wall, local interstitium, and some arteriolar walls (PAS staining, 200x). (D) Diffused mesangial broadening, with the basement membrane thickened segmentally, no absence of spike formation and no eyelash-like changes in the glomerular basement membrane (PASM staining, 400x). (E) Positive staining of Congo red of glomeruli, partial arteriole walls, and local interstitium (Congo red staining, 200x). (F) Pathological apple-green birefringence under cross-polarized light (200x). (G) Fine granular deposition of phospholipase A2 receptor along the capillary walls (immunohistochemistry, 400x). (H) Amyloid-associated protein was negative in the mesangial area of the glomeruli and arteriolar wall, as well as in the focal renal interstitium (immunohistochemistry, 200x). (I) Amyloid-associated protein staining positive control (immunohistochemistry, 200x).
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F1
Light microscopy showed 38 glomeruli, one was spherical sclerosis, whereas in the remaining glomeruli, there was small amounts of erythrophilin deposition under the epithelial cells (Figures 1A,B). The glomeruli had diffused mesangial broadening, and an eosinophilic homogeneous non-structural substance was found to be deposited diffusely in mesangial areas and capillary walls (Figure 1C). The basement membrane thickened segmentally, but there were no absence of spike formation and no eyelash structure in the glomerular basement membrane (GBM) (Figure 1D). Small amounts of eosinophilic homogeneous non-structural deposits were observed in the interstitium and in some arteriole walls, with slight thickening of some arterioles (Figure 1C). Congo red staining showed that the glomeruli, partial arteriole wall and local interstitium were positive (Figure 1E). Pathological apple-green birefringence was produced under cross-polarized light (Figure 1F). Immunohistochemistry showed positive expression fine granular deposition of PLA2R along the capillary walls (Figure 1G). Immunohistochemical staining of paraffin sections showed that amyloid-associated protein (AA) was negative in the mesangial area of the glomeruli and arteriolar wall, as well as in the focal renal interstitium (Figures 1H,I is the positive control).
Pathological features of immunofluorescence. (A) Granular deposition of IgG (+++) along the glomerular capillary walls (immunofluorescence, 400x). (B) Deposits of lambda (++) along the arterioles, mesangial glomeruli, and capillary walls (immunofluorescence, 400x). (C) Deposits of kappa (+) along the glomerular capillary walls (immunofluorescence, 400x). (D) Weak positive of IgG1 deposition in the glomerular basement membrane (immunofluorescence, 400x). (E) IgG2 was negative in the glomerular basement membrane (immunofluorescence, 400x). (F) IgG3 was negative in the glomerular basement membrane (immunofluorescence, 400x). (G) Positive of IgG4 deposition in the glomerular basement membrane (immunofluorescence, 400x). (A-C) Show the immunofluorescence of frozen section, and (D-G) show the immunofluorescence of paraffin section.
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F2
Immunofluorescence showed granular deposition along the glomerular capillary wall with very strongly positive for IgG (Figure 2A), strongly positive for IgM, slightly positive for IgA, and negative for C3, C4, C1q, and fibrinogen. The small arteries, glomerular mesangial area, and capillary walls were strongly positive for lambda (Figure 2B), with kappa deposits observed along the glomerular capillary walls (Figure 2C). Immunofluorescence of IgG subtypes in paraffin sections showed that IgG1 weak positive (Figure 2D), IgG2 and IgG3 negative (Figures 2E,F), IgG4 positive deposit in the GBM (Figure 2G).
Renal pathological features of electron microscopy. (A) Massive electron dense deposition in the subepithelial and basement membranes, and extensive fusion of epithelial podocytes (electron microscopy, 6,000x). (B,C) Scattered fibrous deposits in the mesangial region, basement membrane, and interstitium of the kidney (electron microscopy, 25,000x and 30,000x, respectively).
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F3
Electron microscopy indicated that massive electron dense deposition in the glomerular subepithelial and GBM, and extensive fusion of epithelial podocytes (Figure 3A). It also showed the absence of cellular broadening in the GBM and the mesangial area of the glomeruli, along with disorderly deposits of fibrous material (Figures 3B,C). The renal interstitium had the same characteristic deposition of fibrous material (Figure 3B).