PMC8520974_01
Histological features of the patient. (A-C): Microphotographs of the native kidney. (A) Light microscopy image of a periodic acid-Schiff-stained section showing mesangial proliferation and thickening of the glomerular capillary walls, i.e., membranoproliferative glomerulonephritis pattern. Swelling of glomerular endothelial cells is also seen. (B) Immunofluorescence staining for immunoglobulin G showing only faint deposition in the glomeruli. (C) An electron microscopy section showing no obvious electron-dense deposits. Podocyte foot process effacement is shown (yellow asterisk). (D-N): Microscopic findings of the autopsy samples. (D) Light microscopy image of a periodic acid-Schiff-stained transplanted kidney section showing prominent swelling of glomerular endothelial cells, mesangiolysis, and duplication of the glomerular capillary walls suggesting thrombotic microangiopathy. Peritubular capillaritis is also shown (yellow arrows). A higher magnification image of a periodic acid-Schiff-stained transplanted kidney section demonstrating endothelial swelling (yellow arrows) as well as mesangiolytic lesions (yellow asterisks, E) and a periodic acid-methenamine-silver-stained transplanted kidney section clearly showing duplication of the glomerular capillary walls (yellow arrows, F). Immunofluorescence staining showing weak deposition of immunoglobulin G (G) and complement C3 (H) in the glomeruli. Electron microscopy sections showing swelling of glomerular endothelial cells and double contours of the glomerular basement membrane (I) and widening of the subendothelial space (J). Immunoperoxidase staining for CD42b of the bone marrow tissue showing an increase in megakaryocytes (K). Silver staining of the bone marrow tissue demonstrating mild reticulin myelofibrosis (yellow arrows in L). (M) Atrophic germinal centers (yellow circles) with proliferation of the dilated capillaries in the interfollicular areas (yellow asterisks) were seen in the mildly enlarged lymph nodes (hematoxylin and eosin stain). A higher magnification image of the lymph node showing germinal centers penetrated by hyalinized vessels (hematoxylin and eosin stain, N).
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In addition, renal biopsy showed membranoproliferative glomerulonephritis (MPGN) pattern of injury with few immune deposits (Figures 1A-C). The transplanted kidney weighed 420 g, and microscopically showed thrombotic microangiopathy (TMA): there were prominent swelling of glomerular endothelial cells, mesangiolysis, and duplication of the glomerular capillary walls (Figures 1D-F). Immunofluorescence staining showed focal deposition of Igs and complements (Figures 1G,H). Electron microscopy sections demonstrated glomerular endothelial swelling and widening of the subendothelial space, as well as double contours of the glomerular basement membrane (Figures 1I,J). The bone marrow showed mild hyperplasia with mild reticulin fibrosis, and there was an increase in megakaryocytes (Figures 1K,L). Several lymph nodes were mildly enlarged, and atrophic germinal centers with proliferation of the dilated capillaries in the interfollicular areas were observed (Figure 1M). Germinal centers were penetrated by hyalinized vessels, but neither atypical lymphocytes nor plasma cells were found (Figure 1N).