PMC9522906_01
Massive immune complex depositions on the tubular basement membrane (TBM), fixing IgG and C1q, without active glomerulopathy, with mild tubulointerstitial repercussions. Immunohistochemistry for IgG1, IgG2, IgG3, IgG4, and electron microscopy study in tubular basement membrane. (A) Optical microscopy (OM) - Fuchsinophilic deposits in the TBM (arrows) of atrophic tubules next to normal glomerulus (Masson's trichrome stain, original magnification x 400); (B) OM - Fuchsinophilic deposits in the TBM (arrows) of normal tubules next to normal glomerulus (Masson's trichrome stain, original magnification x 400); (C) Immunofluorescence (IF) - Positivity with IgG antiserum in the TBM of tubules next to glomerulus with mild positivity (original magnification x 200); (D) IF - Positivity with C1q antiserum in the TBM of tubules next to negative glomerulus (original magnification x400); (E) TBM positive staining by immunohistochemistry for IgG1; (F) TBM positive staining by immunohistochemistry for IgG2; (G) TBM positive staining by immunohistochemistry for IgG3; (H) TBM positive staining by immunohistochemistry for IgG4. (I) Transmission electron microscopy of the paraffin-embedded tissue shows immune complex deposits (arrow) in TBM. (E-H): barr = 10 mum. (I): barr = 0.5 mum.
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F1
Mild foci of interstitial fibrosis and tubular atrophy were detected; however, a remarkable finding of granular fuchsinophilic hyaline deposits in the tubular basement membrane (TBM) was observed (Figures 1A,B). TBM, in addition to deposits of IgG with mild positivity in the mesangium of the adjacent glomerulus (Figures 1C,D). Immunohistochemical studies revealed predominant deposition of IgG1 and IgG2, but not IgG3 and IgG4 in the TBM (Figures 1E-H). The kidney biopsy showed normal staining for cubilin using a polyclonal antibody along the apical membrane of the tubular epithelium, but tubular basement membrane staining was not detected (Figure 2A). The patient had serum IgG anti-brush border antibody (ABBA) non-reactive to the proximal tubular brush border on sections of normal human kidney (Figure 2B).
(A) The kidney biopsy shows normal staining for cubilin using a polyclonal antibody along the apical membrane of the tubular epithelium (black arrows), but tubular basement membrane staining was not detected (white arrow). (B) ABBA negative serum stains in proximal tubular epithelial brush border using a normal human kidney tissue (indirect immunofluorescence).
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F2
TBM (Figures 1E-H). The kidney biopsy showed normal staining for cubilin using a polyclonal antibody along the apical membrane of the tubular epithelium, but tubular basement membrane staining was not detected (Figure 2A). The patient had serum IgG anti-brush border antibody (ABBA) non-reactive to the proximal tubular brush border on sections of normal human kidney (Figure 2B).
Proteinuria (mg/24 h) Timeline.
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F3
At 12 months, the patient showed complete remission of proteinuria (Figure 3) and improved renal function (Figure 4).
Creatinine (mg/dL) Timeline.
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F4
At 12 months, the patient showed complete remission of proteinuria (Figure 3) and improved renal function (Figure 4).