PMC9106512_01
Histological findings of the renal specimen. Light microscopy image showing infiltration of inflammatory cells in the interstitial area and a severe degree of interstitial fibrosis and tubular atrophy (about 60%) but without granulomas ((a): PAS staining, original magnification x100). Among the interlobular arteries, some show inflammatory cell infiltration in the lumen ((b): black arrow, hematoxylin and eosin staining, original magnification x400), fibrin deposition in the vascular wall, and rupture of the elastic fibers ((c): white arrow, PAS staining, original magnification x400). There are no significant abnormal findings in the glomerulus, including membrane changes ((d): periodic acid-methenamine silver staining, original magnification x400). As shown in the micrograph of fluorescence immunostaining ((e): original magnification x400), glomerular capillary deposits are dominant in IgG4. PLA2R and THSD7A are negative, suspicious of a secondary pathology. Electron microscopy image ((f): original magnification x3000) showing subepithelial electron-dense deposits (EDDs) and a thickened basement membrane with spike formation (arrow). EDDs are limited to the subepithelium and are relatively uniform in size and distribution, which is not a finding of a secondary pathology.
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fig1
Percutaneous renal biopsy was performed 8 days after PSL administration, wherein light microscopy findings (Figures 1(a)-1(d)) showed 41 glomeruli without crescentic formation or apparent membrane changes. Fluorescence immunostaining (Figure 1(e)) further showed dominant granular to linear glomerular capillary deposits in IgG4; however, PLA2R and THSD7A were negative. Electron microscopy (Figure 1(f)) showed subepithelial electron-dense deposits (EDDs) and a thickened basement membrane with spike formation.