Fibrillary glomerulopathy, non-amyloidotic.
Ultrastructural examination was performed on tissue initially received in histocon media and subsequently fixed in Karnovsky's fixative, resulting in some degree of autolytic change. The ultrastructural examination of one glomerulus demonstrated focal areas of fusion and microvillous transformation of podocyte processes. The mesangium was markedly expanded by increased matrix and mesangial cell processes, which at higher magnification was composed of haphazardly oriented cylindrical non-branching fibrils of variable lengths, each approximately 20 nm in diameter. The fibrils had no internal substructure. The glomerular basement membranes were focally and non-uniformly thickened by a combination of increased basement membrane material, in addition to fibrillar material similar to that previously described in the mesangium. The capillary endothelial cells appeared normal.
Sparse fibrillary material was present in rare tubular basement membranes and an arteriole, but not in an artery examined ultrastructurally.