case_images: PMC11045883_01
case_images: (A) Light microscopy shows segmental thickening of the glomerular basement membrane with segmental double-track sign (Periodic acid-Schiff staining: magnification x100). (B) Light microscopy shows infiltraton of interstitial inflammatory cells (hematoxylin-eosin staining: 200x magnification x100). (C) Electron microscopy shows the deposition of a massive electron-dense substance and the formation of a double-track sign in the subcutaneous layers (red arrow). (D) Electron microscopy shows that the cells in segmental capillaries were increased and swollen with lysosomes.
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case_images: PMC11045883_01_fmed-11-1161560-g001.jpg
case_images: fig1
case_images: In the remaining glomeruli mesangial cells diffuse proliferation with mesangial matrix segmental expansion, mesangial interposition into the capillary walls, and segmental swelling of the endothelial cells was found (Figure 1A). The localized focal renal interstitium showed lymphoid and macrophage infiltration and mild fibrosis (Figure 1B). Electron microscopy of the glomeruli revealed segmental insertion, segmental endothelial cell hyperplasia and swelling with an increased amount of lysosomes, bulk electron-dense deposition in the segmental subendothelium and subsegmental epithelium, no specific tangible structures, and segmental thickening of the glomerulus basement membrane with segmental double track sign (Figure 1C). Interstitial edema, infiltration of lymphocytes and mononuclear cells, and collagen fiber hyperplasia were observed (Figure 1D).
case_images: (A) Neck mass. (B) Lumbar mass. (C) Anterior tibia mass.
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case_images: PMC11045883_01_fmed-11-1161560-g002.jpg
case_images: fig2
case_images: On March 20, 2021, the patient began to experience pain and showed development of skin masses on the neck, lumbar region, and anterior tibia (Figures 2A-C).
case_images: (A-C) Under IF, IgM and kappa light chain were deposited in mesangial area and vascular loops (green), where lambda light chain was negative (FITC direct immunofluorescence:magnification x400). (D) Electron microscopy showed kappa light chain (++ to +++) in glomerular subendothelial and subepithelial deposition. (E) Electron microscopy shows lambda light chain (+-).
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case_images: PMC11045883_01_fmed-11-1161560-g003.jpg
case_images: fig3
case_images: IgA (-), IgM (++), IgG (-), C3 (++ to +++), C4 (-), C1q (-), F (-), kappa (++), and lambda (+-) (Figures 3A-C). Immunoelectron microscopy suggested that glomerular subendothelial and subepithelial deposition and presence of lysosomes in endothelial cells, with kappa (++ to +++) and lambda (+-) (Figures 3D,E).
case_images: Multiplex immune fuorescence staining of glomerular (FITC indirect immunofluorescence:magnification x400). (A) Nucleoplasm (blue). (B) IgM light chainstaining (green). (C) Kappa light chain (red). (D) IgM and kappa light chain. (E) IgM, kappa light chain and nucleoplasm.
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case_images: PMC11045883_01_fmed-11-1161560-g004.jpg
case_images: fig4
case_images: At the same time, we performed multiple immunofluorescence staining, and in this case, IgM and kappa light chain co-located well (Figures 4A-E).
case_images: Clinical course of the patient after admission. Creatinine (Cr); 24 h urinary protein quantification (UTP); serum albumin (ALB); complement 3 (C3); complement 4 (C4); immunoglobin A (IgA); total immunoglobin G (IgG); immunoglobin M (IgM).
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case_images: PMC11045883_01_fmed-11-1161560-g005.jpg
case_images: fig5
case_images: Figure 5 shows the clinical course of the patient.