Glomerular Diseases

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Glomerular Structure & Insult - The Kidney's Sieve

  • Filtration Barrier (📌 E-B-P): Three critical layers.
    • Endothelium (fenestrated): First size barrier.
    • Basement Membrane (GBM; Type IV collagen, heparan sulfate): Negative charge (-ve) repels albumin; second size/charge barrier.
    • Podocytes: Foot processes with slit diaphragms (nephrin, podocin); final size barrier.
  • Mesangium: Intraglomerular cells providing structural support, phagocytosis, and matrix modulation. Glomerulus Anatomy: Filtration Barrier & Mesangial Cells
  • Basic Pathological Responses: Common reactions to injury.
    • Hypercellularity: Increased cells (endothelial, mesangial, epithelial, inflammatory).
    • GBM Thickening: Immune deposits or increased matrix synthesis.
    • Sclerosis: Increased collagenous matrix, scarring.
    • Hyalinosis: Eosinophilic, glassy material deposition.
  • Key Immune Mechanisms of Injury:
    • Immune Complex (IC) Deposition: Location is key (subepithelial, subendothelial, mesangial).
    • Anti-GBM Antibody Disease.
    • Pauci-immune Injury (often ANCA-associated).

⭐ Effacement (flattening) of podocyte foot processes is a characteristic finding in nephrotic syndrome, leading to massive proteinuria.

Nephrotic Syndrome - Protein Spill Crisis

  • Definition: Clinical tetrad: Hypoalbuminemia (<3g/dL), Edema, Hyperlipidemia, & Heavy Proteinuria. 📌 Mnemonic: Proteinuria, Lipids (Hyper-), Edema, Hypoalbuminemia (PLEH).
  • Proteinuria Criteria:
    • Adults: >3.5 g/24h; $U_{P/Cr}$ >3 mg/mg.
    • Children: >40 mg/m²/hr; $U_{P/Cr}$ >2-3 mg/mg.
  • Pathophysiology: Podocyte damage → ↑ glomerular permeability → massive protein loss.
  • Key Features:
    • Edema: Periorbital, pitting; anasarca (↓ oncotic pressure, Na⁺ retention).
    • Hyperlipidemia & Lipiduria: ↑ hepatic synthesis; oval fat bodies ("Maltese cross").
    • Hypercoagulability: Loss of Antithrombin III, Protein C/S. Risk: DVT, RVT.
    • Infection Risk: ↓ IgG.
  • Primary Causes:
    • Children: Minimal Change Disease (MCD).
    • Adults: FSGS, Membranous Nephropathy (MN). Maltese Cross in Urine Microscopy

⭐ Renal vein thrombosis is a classic complication, particularly in Membranous Nephropathy.

Nephritic Syndrome - Inflammatory Glom-Jam

  • Hallmarks: Hematuria (cola-colored urine, dysmorphic RBCs, RBC casts), HTN, oliguria/anuria, azotemia, edema, mild proteinuria (<3.5 g/day). 📌 Mnemonic: PHAROH (Proteinuria, Hematuria, Azotemia, RBC casts, Oliguria, HTN).
  • Pathophysiology: Inflammatory glomerular injury.
  • Common Causes:
    • Post-Streptococcal GN (PSGN)
    • IgA Nephropathy (Berger's)
    • Lupus Nephritis (proliferative types)
    • ANCA-associated vasculitis (e.g., GPA, MPA)
    • Anti-GBM Disease (Goodpasture's) Post-streptococcal Glomerulonephritis Overview
  • Rapidly Progressive GN (RPGN): Clinical emergency! >50% crescents on biopsy.
    • Type I: Anti-GBM (Linear IF)
    • Type II: Immune Complex (Granular IF) - e.g., PSGN, IgA, Lupus
    • Type III: Pauci-immune (Negative IF) - e.g., ANCA vasculitis

⭐ PSGN typically presents 1-2 weeks post-pharyngitis or 3-6 weeks post-impetigo. Serum C3 is ↓, ASO titre ↑.

Systemic Disease & Glomeruli - Body's Civil War

  • Lupus Nephritis (SLE): IC deposition. "Full house" IF (IgG, IgA, IgM, C3, C1q). Class IV (DPGN) common, severe.
  • Diabetic Nephropathy: Top ESRD cause. Kimmelstiel-Wilson nodules. Earliest: microalbuminuria. ACEi/ARBs renoprotective.
  • ANCA Vasculitis (GPA, MPA): Pauci-immune GN, RPGN (crescents). c-ANCA (GPA), p-ANCA (MPA).
  • Amyloidosis: Congo Red: apple-green birefringence. AL/AA types. Nephrotic syndrome common.
  • Goodpasture's Syndrome: Anti-GBM Ab. Affects lungs & kidneys. Linear IgG on IF. Glomerular pathology in systemic diseases

⭐ In Diabetic Nephropathy, Kimmelstiel-Wilson nodules (nodular glomerulosclerosis) are pathognomonic.

High‑Yield Points - ⚡ Biggest Takeaways

  • Nephrotic Syndrome: Proteinuria >3.5g/day, hypoalbuminemia, edema, hyperlipidemia.
  • Minimal Change Disease: Most common in children; podocyte effacement on EM.
  • Membranous Nephropathy: Most common in adults; anti-PLA2R antibodies often present.
  • IgA Nephropathy (Berger's): Most common GN; recurrent gross hematuria with URIs.
  • Post-Streptococcal GN: 1-3 weeks post-infection; subepithelial humps, ↓C3, nephritic.
  • RPGN: Characterized by glomerular crescents and rapid loss of kidney function.
  • Alport Syndrome: X-linked; Type IV collagen defect; hematuria, deafness, ocular lesions.

Practice Questions: Glomerular Diseases

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All are seen in Nephrotic syndrome except

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Flashcards: Glomerular Diseases

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Nephrotic syndrome results in _____, which manifests as pitting edema and secondary hyperaldosteronism

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Nephrotic syndrome results in _____, which manifests as pitting edema and secondary hyperaldosteronism

hypoalbuminemia

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