Overview
This lecture focuses on the comparative pathology, microscopic features, and clinical aspects of primary and secondary glomerulonephritis, with detailed explanations on types, pathogenesis, and diagnostic findings.
Key Types of Primary Glomerulonephritis
- APGN/PSGN (Acute/Post-Streptococcal Glomerulonephritis): Antigen-antibody complexes against planted bacterial antigens cause sub-epithelial "hump-shaped" deposits.
- RPGN (Rapidly Progressive Glomerulonephritis): Has type 1 (Goodpasture's, anti-GBM, intra-membranous), type 2 (immune complex, sub-epithelial), and type 3 (cell-mediated, no deposits).
- MCD (Minimal Change Disease): Normal on light microscopy; electron microscopy shows podocyte foot process effacement; no immune deposits.
- Membranous GN: Diffuse thickening of glomerular basement membrane, sub-epithelial spike-shaped deposits, associated with autoantibodies against podocyte GP330.
- Membranoproliferative GN (MPGN): Basement membrane thickening and hypercellularity; type 1 (sub-endothelial deposits), type 2 (intra-membranous), type 3 (anywhere); tram-track appearance.
Other Primary Glomerulonephritis
- FSGN/GS (Focal Segmental Glomerulonephritis/Sclerosis): Some glomeruli partly affected; either hypercellular (FSGN) or sclerosed (FSGS).
- IgA Nephropathy (Berger’s): IgA immune complex deposits in mesangium, presents after respiratory/GI infection, most common GN worldwide.
- Chronic GN: End-stage, small granular kidneys, glomeruli are hyalinized, tubular atrophy, arteriosclerosis, interstitial chronic inflammation.
Secondary Glomerulonephritis: Diabetic Nephropathy
- Diffuse Diabetic Glomerulosclerosis: Hyaline deposits in mesangium, basement membrane, capillary cap, Bowman's capsule (capsular drops).
- Nodular (Kimmelstiel-Wilson) Lesions: Spherical hyaline masses in glomerulus, pathognomonic for diabetes.
- Other Findings: Hyaline arteriolosclerosis in vessels, tubular vacuolization (Armanni-Ebstein change).
Microscopy & Diagnostic Patterns
- Light Microscopy: Distinct findings for each GN type (hypercellularity, thickening, sclerosing, duplication/tram-track).
- Electron Microscopy: Determines location/shape of deposits (sub-epithelial, intra-membranous, sub-endothelial, mesangial).
- Immunofluorescence: Most GNs are IgG+C3 positive except IgA nephropathy.
Clinical Patterns
- Nephritic Syndrome: Hematuria, mild proteinuria, hypertension (APGN, RPGN).
- Nephrotic Syndrome: Heavy proteinuria, edema, hypoalbuminemia (MCD, FSGS, membranous GN).
- Some types may present with both (MPGN, IgA nephropathy).
Key Terms & Definitions
- Sub-epithelial deposit — Deposit beneath podocytes, seen in membranous GN and PSGN.
- Tram-track appearance — Double contour splitting of basement membrane in MPGN.
- Crescent — Accumulation of cells in Bowman’s space, hallmark of RPGN.
- Kimmelstiel-Wilson nodule — Nodular glomerulosclerosis in diabetic nephropathy.
- Mesangial deposit — Immune complex in mesangium, typical for IgA nephropathy.
Action Items / Next Steps
- Revise comparative tables of nine glomerulonephritis types.
- Draw schematic diagrams highlighting deposit locations and light microscopy features.
- Attend next lecture for further coverage of secondary and hereditary glomerulonephritis, and renal tumors.
- Review lecture recordings if any topics were missed.