PMC6064702_01
The renal biopsy findings in Case 1. a: Light microscopy of the first renal biopsy specimen revealed endocapillary glomerulonephritis (large arrow) and thrombi in the glomerular capillaries (small arrow). Inset: On immunohistochemistry, leukocytes in the glomerular tufts were positive for CD68, which was expressed by tissue monocytes and macrophages (arrow). b: Light microscopy of the second renal biopsy specimen. c: Immunofluorescence microscopy demonstrated granular deposits of IgM along the glomerular basement membrane (GBM) and in the mesangium (arrow). d: Electron microscopy of first renal biopsy showed massive electron-dense deposits in the subendothelial region. e: Electron microscopy of the second renal biopsy
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Huge thrombus-like subendothelial deposits were also detected (Fig. 1a). C3, and kappa light chain in the mesangial region and along the capillary walls. C1q was weakly positive, but IgG, IgA, and lambda light chain were negative (Fig. 1c). Electron microscopy (EM) revealed huge electron-dense deposits in the mesangial region and the subendothelial space, but microtubular structures were not identified (Fig. 1d). In comparison to the findings at the time of the first biopsy, the endocapillary glomerular lesions, which included thrombus-like deposits, was observed to have progressed on LM (Fig. 1b); however, IF and EM showed the same features as before (Fig. 1e).
The clinical course of Case 1.
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Treatment with rituximab (580 mg weekly for 4 weeks) was initiated in August 2016, but his proteinuria persisted and his leg edema became more severe (Fig. 2). In response to this treatment, the patient's proteinuria decreased to 1.7 g/day (Fig. 2).
PMC6064702_02
The renal biopsy findings in Case 2. a: Light microscopy of the first renal biopsy specimen showed the proliferation of mesangial matrix and thrombi in the glomerular capillaries (arrow). The inset shows CD68. b: Light microscopy of the second renal biopsy specimen. c: Immunofluorescence microscopy displayed granular deposits of IgM along the GBM and in the mesangium (arrow). The arteriolar deposition of C3 seems apparent (arrow), which may show microscopic findings of vasculitis. d: Electron microscopy of the first renal biopsy specimen revealed massive subendothelial electron-dense deposits. e: Electron microscopy of the second renal biopsy specimen.
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C3 and C1q were also weakly positive, but IgG and IgA were not detected (Fig. 3c). EM revealed huge electron-dense deposits in the mesangial region and subendothelial space, but microtubular structures were not confirmed (Fig. 3d). The huge thrombus-like subendothelial deposits that were noted in the first biopsy specimen were seen in the second renal biopsy specimen (Fig. 3b). The IF and EM findings were largely the same as those at the first biopsy (Fig. 3e).
The clinical course of Case 2.
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His proteinuria decreased to 3.2 g/day, but his renal function showed deterioration (Fig. 4).