What is Membranous glomerulonephritis?

Glomerulonephritis characterized by diffuse thickening of glomerular capillary basement membranes, due in part to subepithelial deposits of immunoglobulins separated by spikes of basement membrane material, and clinically by an insidious onset of the nephrotic syndrome and failure of disappearance of proteinuria; the disease is most commonly idiopathic but may be secondary to malignant tumors, drugs, infections, or systemic lupus erythematosus.