Underlying IgM heavy chain amyloidosis in treatment-refractory IgA nephropathy: A case report

Figure 2 Second renal biopsy manifestations. A: Light microscopy showed well-opened capillary loops and mild pale eosinophilic material in the mesangium and basement membranes (hematoxylin and eosin stain, 400 ×); B: Thickened GBM with subepithelial fringe-like projections (red arrow) (periodic acid-Schiff-methenamine stain, 400 ×); C: Congo red stain was greenish under polarized light (white arrow, 100 ×), involving an afferent glomerular arteriole; D: Immunofluorescence showed deposits of IgM in the mesangium and small vessels (200 ×). κ and λ were also positive (not shown); E and F: Electron microscopy showed randomly oriented amyloid fibrils along glomerular capillary walls (blue arrow).