The tissue examined for light microscopy consists of renal cortex, including the portion of the renal capsule, and medulla. The profiles of up to 32 glomeruli are identified in the paraffin embedded, frozen and plastic embedded tissues, of which 12 (37%) are obsolescent. The remaining glomeruli are normocellular and show abundant Congo red positive, thioflavin-T positive, waxy, eosinophilic material expanding the mesangial areas and capillary walls, with focal nodularity consistent with amyloid. On silver stain, focal subepithelial spikes corresponding to the areas of subepithelial amyloid are noted. There are no necrotizing lesions or crescents. There is extensive amyloid deposition present also in intrarenal arteries and arterioles. An immunoperoxidase panel shows the amyloid to have positive staining for amyloid P (precursor protein present in all forms of amyloid) and amyloid A (amyloid occurring with chronic inflammatory states), with negative staining for kappa and lambda light chains and transthyretin (prealbumin) (data not shown). There is widespread tubular atrophy and corresponding interstitial fibrosis. No active vasculitis is seen.
ELECTRON MICROSCOPIC EXAMINATION