Master Membranoproliferative Glomerulonephritis with Picmonic for Medicine

Membranoproliferative glomerulonephritis (MPGN) is a type of nephritic-nephrotic kidney disorder characterized by alterations in the glomerular basement membrane, proliferation of glomerular cells, and leukocyte infiltration. In most cases of type I MPGN, there is evidence of immune complex deposition in the glomerulus with activation of both the classical and alternative complement pathways.

Specifically, type I MPGN is characterized by the presence of discrete subendothelial immune complexes.

In many cases, the antigens involved in MPGN are thought to be derived from infectious agents such as hepatitis C and hepatitis B viruses. Although both hepatitis C and hepatitis B are associated with MPGN, the associations with hepatitis C are stronger while hepatitis B is more closely associated with membranous glomerulonephritis.

Immunofluorescence demonstrates a granular pattern of C3 deposition.

A glomerular basement membrane that is thickened and the glomerular capillary wall often shows a tram-track appearance caused by duplication, commonly called splitting, of the basement membrane by ingrowth of the mesangium. This can be seen on light microscopy, through silver stain or H&E stain, as well as looking for mesangial deposits on electron microscopy.

Electron microscopy shows a glomerular basement membrane that is thickened and the glomerular capillary wall often shows a tram-track appearance caused by duplication, commonly called splitting, of the basement membrane by ingrowth of the mesangium.

Type II MPGN, also called dense deposit disease, has abnormalities that suggest activation of the alternative pathway.

Type II MPGN, also called dense deposit disease, has abnormalities that suggest activation of the alternative pathway. It is called dense deposit disease due to deposition of dense material of unknown composition in the glomerular basement membrane.

More than 70% of patients have a circulating antibody called C3 nephritic factor, which is an autoantibody that binds to the C3 convertase in the alternative pathway. C3 nephritic factor binding causes stabilization of the convertase, protecting it from enzymatic degradation and therefore favors persistent C3 activation and hypocomplementemia.