Fig. 2

Pathological findings on the second renal biopsy. a, b and c Mass- and particle-like depositions of IgG, IgG4, and C3 along the mesangial area and capillary wall (immunofluorescence assay). d, e and f Mildly diffuse proliferation of glomerular mesangial cells and interstitial cells, moderate aggravation of focal segmental lesions, diffuse thickening of basement membrane (along with diffuse spike formation), subepithelial and mesangial deposition of fuchsinophilic protein, vacuolar and granular degeneration of renal tubular epithelial cells, multifocal loss of brush border, dilation of the renal tubules, multifocal atrophy, diffuse infiltration of lymphocytes, monocytes, and plasma cells in renal interstitium, multifocal fibrosis, and thickening of small arterial wall (light microscopy: HE, Masson, and PASM staining, × 200). g and h Immunohistochemical staining of IgG and IgG4. i Proliferation of glomerular mesangial cells and interstitial cells, diffuse and irregular thickening of basement membrane, electron-dense deposits in the subepithelial, intrabasal, subendothelial, and mesangial areas, diffuse fusion of the foot processes among epithelial cells, detachment and partial atrophy of the microvilli of renal tubular epithelial cells as well as edema, infiltration of lymphocytes/monocytes, and fibrosis in renal interstitium. Red Arrow: electron-dense deposits; Blue arrow: diffuse fusion of the foot processes among epithelial cells(electron microscopy, × 6000)