Membranous glomerulonephritis is an antibody mediated disease in which the immune complexes localize to the subepithelial aspect of the capillary loop. That is, between the outer aspect of the basement membrane and the podocyte (epithelial cell)
.
The immune complexes develop in situ or, less likely, by the deposition of circulating immune complexes. The antibody may bind to an intrinsic glomerular antigen or to an exogenous antigen planted on the capillary wall.
Approximately 25 to 30% of cases are secondary. Common associations include:
Membranous glomerulonephritis is more common in adults and most patients are older than 30 years at diagnosis. Membranous glomerulonephritis accounts for 35-50% of cases of adult nephrotic syndrome. Most patients present with heavy proteinuria, most commonly in the nephrotic range, that is insidious in onset. A few patients have accompanying microscopic hematuria.
A. Morphologic Features
By light microscopy the capillary loops appear thickened and rigid with numerous small subepithelial spikes and pinholes noted on the silver stain.
Granular subepithelial deposits of IgG and C3 are seen on direct immunofluorescence microscopy.
Subepithelial electron dense deposits are present ultrastructurally. The deposits may become incorporated into the basement membrane (intramembranous) and are eventually reabsorbed.
B. Clinical Course
The course of untreated idiopathic membranous glomerulonephritis is variable.
Of patients presenting with the nephrotic syndrome and a normal serum creatinine:
Twenty to 25% of patients progress to end-stage renal failure over a 20 to 30 year follow-up. Patients in whom a causitive agent is identified, usually respond to treatment of the underlying disorder, or withdrawl of the offending agent.
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Last Modified: February 26, 1997