VACUOLIZATION OF THE GLOMERULAR BASEMENT MEMBRANE

Immunofluorescence and clinical data were collected retrospectively and renal tissue was examined by electron microscopy 1) for 20 consecutive patients whose glomeruli were normal in light microscopy except for vacuolization of obliquely‐cut portions of the glomerular basement membrane (GBM) after periodic acid‐silver‐methenamine staining, and 2) for 10 control patients with completely normal glomeruli in light microscopy. By electron microscopy the biopsies with vacuolization showed two patterns of abnormalities. In pattern 1 (10 patients) the changes corresponded to the GBM changes in membranous glomerulonephritis or resolving acute poststreptococcal glomerulonephritis, further confirmed by immunofluorescence and clinical data. In pattern II (10 patients) the GBM showed indentations and intramembraneous lucent areas very similar to but more sparsely distributed than the changes in pattern I. Patients with pattern II lesions had various renal diseases: systemic lupus erythematosus, minimal changes glomerulonephritis, IgA‐IgG‐glomerulonephritis, graft rejection, and acute anuric tubulointerstitial nephritis, but clinical and immunofluorescence data did not differ from those of the controls. The hypothesis is presented that the indentations and intramembraneous lucent areas in patterns I and II are remnants or former subepithelial deposits.