Membranoproliferative Glomerulonephritis (MPGN)

on 12.12.08 with 0 comments

Know the pathogenesis of type I and type II MPGN
  • Type I - Chronic Immune Complex GN

    • Granular deposits of IgG and C3 in subendothelial and mesangial distributions

    • Activation of classic complement pathway

    • Presence of cryoglobulins and circulating Igs

    • Similar lesions produced in animal studies utilizing foreign serum proteins

  • Type II – Dense deposit disease

    • NOT an immune complex disease

    • Probably due to abnormality in complement metabolism

    • C3 nephritic factor present in the serum

Know the LM, IF, and EM findings of type I and type II MPGN
  • Type I
    • Light Microscopy
      • Diffuse, proliferative GN
      • Thickening of glomerular capillary walls due to subendothelial immune deposits and interposition of mesangial matrix and cells between layers of GBM
      • Seen on silver stain as double contour, splitting, or train track appearance of capillary walls.
      • Increase in mesangial cells and matrix
      • Glomerulus appears lobulated
      • Crescents rare
    • Immuno Fluorescence – Coarsely granular deposits of C3 and often IgG, IgM, C4, properdin, and fibrin in mesangium and peripheral capillary loops
    • Electron Microscopy
      • Dense subendothelial and mesangial deposits
      • Mesangial matrix interposition w/ capillary wall thickening and narrowing of capillary lumen
  • Type II
    • LM
      • Similar to Type I, although crescents are more common
      • Dense deposits seen as PAS+, ribbon-like deposits w/in the capillary wall (i.e., intamembranous) as well as along Bowman’s capsule and tubular membrane.
    • IF – C3 present in deposits, IgG much less commonly found
    • EM – extensive replacement of lamina densa with “very dense deposits”

Know the clinical manifestations and prognosis of MPGN

  • Mainly a disease of children/young adults
    • Exception – association of type I with Hepatitis B infection
  • Nephrotic Syndrome (80%)
  • Acute nephritic syndrome (20%) more common in type I
  • Type II associated with partial lipodystrophy in some patients
  • Poor prognostic signs include
    • Reduced GFR at onset
    • Presence of nephrotic syndrome
    • Early HTN
    • Gross hematuria
    • Presence of crescents or sclerosis on biopsy
  • Recurs in about 25% of transplants, but rarely interferes with function

Know the urinary sediment and renal function of MPGN

  • Shows nephrotic range proteinuria along with nephritic syndromes such as hematuria

  • About 33% develop end-stage renal disease w/in 10 years (type II) or 15-20 years (type I)

  • About 33% have persistent nephrotic syndrome with relatively stable renal function

  • About 33% have persistent non-nephrotic proteinuria and/or hematuria

  • Less than 5% experience spontaneous remission

Category: Pathology Notes



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