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membranoproliferative glomerulonephritis

Wednesday 12 May 2004

Definition : Membranoproliferative glomerulonephritis or MPGN is a type of glomerulonephritis (GN) caused by IgG deposits in the kidney glomerular mesangium and basement membrane (GBM), activating complement and damaging the glomeruli.

The GBM is rebuilt on top of the deposits, causing a "tram-tracking" appearance under the microscope. MPGN accounts for approximately 4% of primary renal causes of nephrotic syndrome in children and 7% in adults.

Examples

- cryoglobuliemia-asscociated glomerulonephritis

Synopsis

- diffuse lobular simplification of glomeruli
- extensive endocapillary proliferation
- mesangial hypercellularity (increased number of cells in mesangium - mesangial cells)
- increased glomerular basal membrane thickness
- extensive double contours of the glomerular basement membranes

  • mesangial interposition
  • new basement membrane formation
  • response to subendothelial immune complex deposits
    • PAS positive and globular-to-sausage shaped deposits

- Immunofluorescence

  • IgG deposits
  • segmental, coarsely granular-to-globular IgG deposits
  • elongated capillary wall IgG deposits
  • subendothelial, segmental, irregular IgG capillary wall deposits
    • smooth outer contour
      • molding against the glomerular basement membrane (type 1)

Etiology

- immune complex-mediated membranoproliferative glomerulonephritis

  • chronic infections

Types

- membranoproliferative glomerulonephritis type 1
- membranoproliferative glomerulonephritis type 2

Ultrastructure

- multiple, large subendothelial deposits
- multiple, small-to-medium subendothelial deposits
- marked endocapillary proliferation (proliferating endothelial and mesangial cells)

  • occlusion of the capillary lumen

- large subendothelial dense immune complex-type deposits

  • subendothelial deposit between the glomerular basement membrane and mesangial cell

- mesangial dense immune complex-type deposits
- mesangial interposition without evident deposits

  • "tram-track" image (double contour of the basement membrane)

- Atlas of renal pathology by Agnes Fogo