case_images: PMC8478360_01
case_images: Microscopic and Immunofluorescence findings. (A) Interstitial inflammatory infiltrate (combination of eosinophils and mononuclear cells; black arrows) associated with tubulitis (red arrows), tubular damage, and interstitial edema. H&E x250. (B) Extensive tubular damage with simplification of tubules lined by flattened cells and interstitial inflammation with tubulitis. H&E x250. (C) and (D) Interstitial inflammation with tubulitis, edema, and tubular damage with eosinophils. H&E x250 in (C) and x500 in (D). (E) Immunofluorescence stain for lambda light chains, fluorescein isothiocyanate (x250) showing intense linear staining along tubular basement membranes and granular staining in the cytoplasm of some proximal tubular cells. (F) Immunofluorescence stain for kappa light chains (x250) with fluorescein isothiocyanate showing no staining in renal parenchyma.
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case_images: The main findings were in the tubulointerstitial compartment which showed evidence of tubular damage and tubulitis (Figure 1A-1D). In contrast, kappa light chain stain was essentially negative (Figure 1E and 1F).
case_images: Electron Microscopy (EM) findings. (A) EM x7500 and (B) EM x12500 - Uranyl acetate and lad citrate stain showing no immune complexes, light chain deposits or fibrillary material. Mild, segmental effacement of the foot processes of visceral epithelial cells. (C) EM x7500 and (D) EM x7500 - Uranyl acetate and lead citrate stain showing apical blebbing, segmental loss of microvillous borders and lysosomes in cytoplasm of proximal tubular cells. (E) EM x12500 and (F) EM x18500 - Uranyl acetate and lead citrate stain showing details of lysosomes in proximal tubular cells. Note moth eaten appearance of lysosomes reflecting partial extrusion of their enzymatic contents.
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case_images: Electron microscopy (EM) revealed interstitial edema and inflammation without any immune complexes, fibrillary material, or light chain deposits in the tubulointerstitial compartment (Figure 2).
case_images: Bone marrow biopsy and aspirate findings. A - Bone marrow biopsy, and B - aspirate analysis showed a plasma cell neoplasm with lambda light chain restriction (H&E x400); C - Prussian blue staining revealed adequate iron storage (x400); D - CD138 stain was positive in increased numbers of plasma cells representing approximately 50% of the marrow cellularity (x400).
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case_images: Bone marrow biopsy and aspirate showed a plasma cell neoplasm with lambda light chain restriction (Figure 3A and 3B). Prussian blue stains of the biopsy revealed adequate iron storage (Figure 3C). CD138 was positive in increased numbers of plasma cells representing approximately 50% of the marrow cellularity (Figure 3D).
case_images: Timeline organizing main events of the case.
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case_images: At the time of writing our case report, the patient had already died (Figure 4).