## Diagnosis: Post-Infectious Glomerulonephritis (PIGN) **Key Point:** The 'hump-like' (or 'humps') subepithelial electron-dense deposits are pathognomonic for post-infectious glomerulonephritis, classically following streptococcal infection. **High-Yield:** Post-infectious GN is the most common cause of acute nephrotic syndrome worldwide, particularly in children and young adults in developing countries including India. The subepithelial 'hump' deposits are a hallmark finding on electron microscopy. ### Pathology Features of Post-Infectious GN | Feature | Finding | |---------|----------| | Light microscopy | Diffuse proliferative GN | | Immunofluorescence | IgG, IgM, C3 (granular pattern) | | Electron microscopy | Subepithelial 'hump-like' deposits | | Typical antecedent | Streptococcal pharyngitis or skin infection | | Serology | Elevated anti-streptococcal antibodies (ASO titre) | **Clinical Pearl:** Post-infectious GN typically presents 1–3 weeks after a streptococcal infection (Group A Streptococcus most common). The majority of cases resolve spontaneously with supportive care; progression to chronic kidney disease is uncommon in children but more frequent in adults. **Mnemonic: HUMPS** — **H**istory of infection, **U**rinary findings (hematuria + proteinuria), **M**ultiple deposits on EM, **P**roliferative on LM, **S**ubepithelial location. ### Why Post-Infectious GN is Most Common in This Context 1. The **subepithelial 'hump' deposits** on electron microscopy are virtually diagnostic of post-infectious GN. 2. Diffuse proliferative pattern on light microscopy is characteristic. 3. In India and developing nations, streptococcal infections remain highly prevalent. 4. Age (35 years) and presentation with acute nephrotic syndrome fit the epidemiology. [cite:Harrison 21e Ch 279]
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