Membranoproliferative glomerulonephritis ( MPGN) causes both a nephrotic and a nephritic syndrome. MPGN is a true nephritis in that there is associated leukocytic infiltration of the glomerulus.
MPGN involves both the membranous and "proliferative" systems of the glomerulus. The membranous system is the shared basement membrane of the endothelium and the epithelium of the visceral layer of Bowman's capsule. The proliferative system refers to the mesangial cells and the mesangial matrix that supports the mesangial cells. In MPGN there is a thickening of the membranous system , along with a proliferation of the mesangial components.
Microscopically, the glomerulus appears hypercellular, swollen and the basewment membrane is thickened. MPGN is found in two variants. In both the mesangial cells invade and split the glomerular basement membrane giving the typical "tram track" appearance. seen in MPGN. Type 1 is due to IgG and C3 deposition, and Type 2 to continous dense deposits in the basement membrane along with C3 deposition. Type 2 is often called "dense deposit disease." It is not possible at this magnification to distinguish type 1 from type 2 .
Note that in this slide the glomerulus is hypercellular and contains more hyaline material than normal. Note also that Bowman's space is obliterated by the enlarged glomerulus.
About 12% of patients with the nephrotic syndrome have MPGN.