Glomerulonephritis classification

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Nephritic vs. Nephrotic - The Great Divide

  • Nephritic (Inflammatory): Glomerular inflammation (immune complex deposition).
    • Presents with: Hematuria (RBC casts), HTN, oliguria, azotemia.
    • Proteinuria: Mild-to-moderate (< 3.5 g/day).
  • Nephrotic (Non-inflammatory): Podocyte damage leading to ↑ permeability.
    • Presents with: Massive proteinuria (> 3.5 g/day), hypoalbuminemia, severe edema, hyperlipidemia/lipiduria (oval fat bodies).
    • 📌 Mnemonic: PALE (Proteinuria, hypoAlbuminemia, Lipidemia, Edema).

Acute Glomerulonephritis Classification and Management

⭐ Nephrotic syndrome causes a hypercoagulable state due to urinary loss of Antithrombin III, increasing risk for thromboembolism.

Nephrotic Syndromes - The Protein Leakers

  • Hallmarks: Proteinuria >3.5 g/day, hypoalbuminemia, severe edema, hyperlipidemia/lipiduria (oval fat bodies).
  • Minimal Change Disease (MCD):
    • Most common cause in children; often follows infection.
    • LM: Normal. EM: Diffuse effacement of podocyte foot processes.
    • Excellent, rapid response to corticosteroids.
  • Focal Segmental Glomerulosclerosis (FSGS):
    • Most common cause in adults (esp. African American).
    • Sclerosis in segments of some glomeruli.
    • Associations: HIV, heroin use, sickle cell, obesity.
  • Membranous Nephropathy (MN):
    • Subepithelial immune complex deposits → "spike and dome" on EM.
    • Associated with anti-PLA2R Abs, HBV, NSAIDs, malignancy.

⭐ In an adult with new-onset nephrotic syndrome, especially Membranous Nephropathy, always consider and screen for an underlying solid tumor (e.g., lung, colon).

EM of podocyte foot process effacement in MCD

Nephritic Syndromes - The Inflammatory Crew

  • Hallmark: Glomerular inflammation & bleeding.
  • Presentation: Hematuria (cola-colored urine), RBC casts, hypertension, oliguria, and mild proteinuria (< 3.5 g/day).

RBC casts and dysmorphic RBCs in urine sediment

Classification by Complement (C3) Levels:

  • Normal C3

    • IgA Nephropathy (Berger's Disease): Most common cause worldwide. Often follows URI/GI infection.
    • Pauci-Immune GN: ANCA-associated (e.g., GPA, MPA).
    • Alport Syndrome: Hereditary (Type IV collagen defect); associated with deafness & ocular findings.
  • Low C3

    • Post-Streptococcal GN (PSGN): Follows GAS infection (1-3 weeks post-pharyngitis, 3-6 weeks post-impetigo).
    • Membranoproliferative GN (MPGN): "Tram-track" appearance on histology.

Exam Tip: IgA nephropathy presents with hematuria syn-pharyngitically (concurrently with infection), while PSGN has a significant latency period after the infection resolves.

Mixed Pictures - Nephritic-Nephrotic Overlap

  • Presents with features of both nephritic (hematuria, HTN) and nephrotic (>3.5 g/day proteinuria, edema) syndromes.
  • Membranoproliferative Glomerulonephritis (MPGN): Thickened glomerular basement membrane (GBM) & mesangial proliferation.
    • Classic "tram-track" appearance on light microscopy.
    • Can be primary or secondary (e.g., HCV, SLE, cryoglobulinemia).
  • Diffuse Proliferative Glomerulonephritis (DPGN): Most common & severe lupus nephritis (Class IV).
    • Features "wire-loop" lesions from subendothelial deposits.

MPGN tram-track appearance (light and electron microscopy)

MPGN Type I is strongly associated with Hepatitis C virus (HCV), while Type II (Dense Deposit Disease) is linked to C3 nephritic factor, an autoantibody that stabilizes C3 convertase, leading to persistent complement activation and low C3 levels.

  • Nephritic syndrome = inflammation (hematuria, HTN). Nephrotic syndrome = podocyte damage (massive proteinuria >3.5 g/day, edema).
  • Linear IgG deposits on immunofluorescence are pathognomonic for Goodpasture's syndrome.
  • Subepithelial "humps" are classic for Post-streptococcal GN.
  • "Spike and dome" appearance on electron microscopy indicates Membranous Nephropathy.
  • Crescent formation signifies Rapidly Progressive Glomerulonephritis (RPGN), a nephrologic emergency.
  • IgA Nephropathy is the most common primary glomerulonephritis worldwide.

Practice Questions: Glomerulonephritis classification

Test your understanding with these related questions

A 21-year-old male presents to your office with hematuria 3 days after the onset of a productive cough and fever. Following renal biopsy, immunofluorescence shows granular IgA deposits in the glomerular mesangium. Which of the following do you suspect in this patient?

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Flashcards: Glomerulonephritis classification

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Diffuse proliferative glomerulonephritis is a common cause of death in patients with _____

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Diffuse proliferative glomerulonephritis is a common cause of death in patients with _____

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