Early glomerular lesions in amyloidosis. Electronmicroscopic findings.

Our investigations on early glomerular changes in renal amyloidosis showed the following: 1. In some renal biopsies, amyloid was demonstrated in the mesangial matrix predominantly and could be seen penetrating through the basement membrane of the mesangial region into the subepithelial space of adjacent glomerular capillaries. 2. In other biopsies, showing the same severity of amyloidosis, deposits were demonstrated in the mesangium and in the capillary walls distant from the mesangium on both sides of the basement membrane. There was no apparent connection between the deposits in these two areas. 3. On the basis of the morphological changes found in the cytoplasm of the mesangial cells, the glomerular epithelial cells and partly also in the endothelial cells, supported by our electron microscopic findings in the immediate vicinity of these cells, we come to the conclusion that amyloid in the glomerulus is formed from amyloid precursors brought via the blood stream. 4. Amyloid fibrils may be formed in the extracellular space of the glomerulus under the influence of lysosomal enzymes released from epithelial, mesangial and perhaps endothelial cells, by action of these enzymes on extracellularly deposited amyloid precursors.