Basement membrane-changes in membranoproliferative glomerulonephritis: a light and electron microscopic study.

This study is based on 31 renal biopsies from 28 patients with idiopathic membranoproliferative glomerulonephritis (MPGN). 18 cases were classified as "pure" MPGN, 10 as lobular GN. For light microscopy two staining procedures were found to be of particular value: Pearse trichrome (PAS+Orange G) and Jones-Chromotrope (methenamine silver + Chromotrope 2R). These techniques reveal conspicuous basement membrane (b.m.) lesions which are not observed in other types of GN and are characterized by thickening of the b.m. and a bright orange or red coloration, respectively, which can well be separated from normal (PAS-positive or argyrophilic) basement membranes. Electron microscopy was performed in 13 cases in order 1. to analyze the fine structure of this lesion, 2. to match the results with the current subclassification concept which is essentially based on the discrimination of intramembranous dense (IMDD) and subendothelial deposits. The typical finding of a continuous intramembranous electron-dense material which proves to be argyrophilic in ultrathin sections was present in 3 (23%) of the cases.