Post-streptococcal Glomerulonephritis (PSGN)
PSGN is a classic example of an immune complex-mediated nephritic syndrome, occurring weeks after a Group A Beta-Hemolytic Streptococcus (GAS) infection of the pharynx or skin.
1. Pathological Features
| Examination | Findings |
|---|---|
| Light Microscopy (LM) | Hypercellular, inflamed glomeruli; enlarged glomeruli with infiltration of neutrophils and monocytes. |
| Immunofluorescence (IF) | “Lumpy-bumpy” pattern of IgG, IgM, and C3 deposition along the GBM and mesangium. |
| Electron Microscopy (EM) | Subepithelial “humps” (immune complex deposits). |
2. Exam Must-Knows
- Timing: Pharyngitis (1–3 weeks) or Skin/Impetigo (3–6 weeks) before the onset of hematuria, hypertension, and periorbital edema.
- Lab Differentiator: Low serum C3 levels (due to consumption of complement) are a key diagnostic marker. ASO or anti-DNase B titers will be elevated.
- Prognosis: Excellent in children (mostly supportive care); adults have a higher risk of developing chronic renal failure.
Pathology Board Hint: For test questions, visualize the classic “Coca-Cola” colored urine in a child who had a sore throat or skin infection a few weeks ago. The presence of low C3 + subepithelial humps is the definitive combination for PSGN.