The word membranous refers to the glomerular basement membrane of the kidney; glomerulonephritis means "a kidney disease affecting the capillaries of the glomeruli"; nephropathy is a generic term that just refers to any disease of the kidney.immune complex. Current research indicates that the majority of the immune complexes are formed via binding of antibodies to antigens in situ to the glomerular basement membrane. The said antigens may be endogenous to (from) the basement membrane, or "planted" from systemic circulation.
The immune complex serves as an activator that triggers a response from the C5b - C9 complements, which form a membrane attack complex (MAC) on the glomerular epithelial cells. This, in turn, stimulates release of proteases and oxidants by the mesangial and epithelial cells, damaging the capillary walls and causing them to become "leaky". In addition, the epithelial cells also seem to secrete an unknown mediator that reduces nephrin synthesis and distribution.glomerular basement membrane (GBM). By light microscopy, the basement membrane is observed to be diffusively thickened. Using Jones' stain, the GBM appears to have a "spiked" or "holey" appearance. On electron microscopy, subepithelial deposits that nestle against the glomerular basement membrane seems to be the cause of the thickening. Also, the podocytes lose their foot processes.
As the disease progresses, the deposits will eventually be cleared, leaving cavities in the basement membrane. These cavities will later be filled with basement membrane-like material, and if the disease continues even further, the glomeruli will become sclerosed and finally hyalinized.
Immunoflourescence microscopy will reveal typical granular deposition of immunoglobulins and complement along the basement membrane.
Perhaps the most difficult aspect of membranous glomerulonpehritis is deciding which patients to treat with immunosuppressive therapy as opposed to simple "background" or anti-proteinuric therapies. A large part of this difficulty is due to a lack of ability to predict which patient will progress to end-stage renal disease, or renal disease severe enough to require dialysis. Because the above medications carry risk, treatment should not be initiated without careful consideration as to risk/benefit profile. Of note, corticosteroids (typically Prednisone) alone are of little benefit. They should be combined with one of the other 5 medications, each of which, along with prednisone, has shown some benefit in slowing down progression of membranous nephropathy. It must be kept in mind, however, that each of the 5 medications also carry their own risks, on top of prednisone.