Fig. 2

Histological features of the renal biopsy showing the endocapillary proliferative glomerulonephritis typical of poststreptococcal acute glomerulonephritis (PSAGN) but with atypical severe tubulointerstitial change. a Periodic acid-Schiff (PAS) staining of formalin-fixed paraffin-embedded tissue (FFPE) sections. Diffuse global endocapillary proliferation with massive infiltration of neutrophils was observed (Scale bar = 20.0 μm). b Chloroesterase staining, which detects neutrophils, confirmed the massive accumulation of neutrophils in glomeruli (Scale bar = 20.0 μm). c Tubulointerstitial lesions with marked infiltration of inflammatory cells were observed. Red arrows indicate the regions of tubulitis, and blue arrows indicate the regions of capillaritis (PAS, Scale bar = 20.0 μm). d Immunofluorescence (IF) microscopy showed granular deposition of C3 mainly along the glomerular capillary walls (Scale bar = 20.0 μm). e Electron microscopy showed many subepithelial electron dense deposits (indicated by blue arrows) with a hump-shaped appearance