Chapter 507 Membranoproliferative Glomerulonephritis
Membranoproliferative glomerulonephritis (MPGN), also known as mesangiocapillary glomerulonephritis, most commonly occurs in children or young adults. MPGN can be classified into primary, idiopathic, and secondary forms of glomerular disease. Secondary forms of MPGN are most commonly associated with subacute and chronic infection, including hepatitis B and C, syphilis, subacute bacterial endocarditis, and infected shunts, especially ventriculoatrial shunts (shunt nephritis). MPGN can also be one of the glomerular lesions seen in lupus nephritis (Chapter 508).
Pathology
MPGN is defined by the histologic pattern of glomeruli as seen by light, immunofluorescence, and electron microscopy. Two subtypes have been defined on histologic criteria and are associated with different clinical phenotypes. Type I MPGN is most common. Glomeruli have an accentuated lobular pattern from diffuse mesangial expansion, endocapillary proliferation, and an increase in mesangial cells and matrix. The glomerular capillary walls are thickened, often with splitting from interposition of the mesangium. Crescents, if present, indicate a poor prognosis. Immunofluorescence microscopy reveals C3 and lesser amounts of immunoglobulin in the mesangium and along the peripheral capillary walls in a lobular pattern. Electron microscopy confirms numerous deposits in the mesangial and subendothelial regions.
Far less common is type II MPGN, also called dense deposit disease, which has similar light microscopic findings as type I MPGN. Differentiation from type I disease is by immunofluorescence and electron microscopy. In type II disease, C3 immunofluorescence typically is prominent without concomitant immunoglobulin. By electron microscopy, the lamina densa in the GBM undergoes a very dense transformation, without evident immune complex–type deposits.
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