Fig. 2
Renal histopathological result showed almost normal glomeruli, massively infiltrating cells, and abundant interstitial fibrosis under the light microscopy. a The glomerulus showed glomerular mesangial cells proliferation and diffuse and irregular thickening of basement membrane (HE staining, × 200). b, c A mass of plasma cells and fibrotic fibers (HE staining, × 400) can be observed in the interstitium. d, e Immunohistological analysis revealed mostly CD20-positive B cells (× 400) and CD138-positive plasma cells (× 400) in the interstitium. f Immunohistochemistry for IgG4 shows abundant positive plasma cells (coloured brown) (× 400)