A 28-year-old man presents with sudden onset hematuria, hypertension (160/100 mmHg), and mild edema 10 days after a sore throat. Urinalysis shows RBC casts and dysmorphic RBCs. Serum creatinine is 1.2 mg/dL. Complement levels are low. Which of the following is NOT a characteristic feature of post-streptococcal glomerulonephritis (PSGN)?

Question

Accepted Answer

D. IgA-dominant immune deposits on immunofluorescence. ## Distinguishing Features of Post-Streptococcal GN

**Key Point:** PSGN is characterized by immune complex deposition (IgG and IgM, NOT IgA) and distinctive electron microscopic findings.

### Immunofluorescence Pattern in PSGN
- **Granular deposits** of IgG and IgM along the glomerular basement membrane and mesangium
- **NOT IgA-dominant** — IgA-dominant deposits are the hallmark of IgA nephropathy (Berger disease), a different entity
- C3 deposits are prominent (C3-dominant pattern)

### Electron Microscopy: Pathognomonic Finding
- **Subepithelial "humps"** — large electron-dense deposits between the GBM and podocytes
- These humps are virtually diagnostic of PSGN and distinguish it from other nephritic GN

### Histology
- Endocapillary proliferation (increased cellularity within capillary loops)
- Extracapillary proliferation (crescent formation) — present in severe cases
- Acute tubular necrosis may occur

### Clinical Course in Children
- Hematuria and hypertension typically resolve within **1–2 weeks**
- Urinary abnormalities may persist for months but eventually clear
- Excellent prognosis in children; adults have higher risk of progression

**High-Yield:** The combination of **subepithelial humps + IgG/IgM/C3 deposits + clinical history of streptococcal infection** is diagnostic of PSGN. IgA-dominant staining points away from PSGN and toward IgA nephropathy.

**Clinical Pearl:** PSGN is the most common acute GN in children worldwide, especially in low-income countries with high streptococcal infection burden.

| Feature | PSGN | IgA Nephropathy |
| --- | --- | --- |
| **IF pattern** | IgG/IgM/C3 (granular) | IgA-dominant |
| **EM finding** | Subepithelial humps | Mesangial deposits |
| **Trigger** | Post-streptococcal | Mucosal infection (IgA1 overproduction) |
| **Prognosis (children)** | Excellent | Variable; some progress |

Answer

A. Rapid resolution of hematuria and hypertension within 1–2 weeks in children

Answer

B. Subepithelial 'humps' on electron microscopy

Answer

C. Proliferation of endocapillary and extracapillary cells

Explanation

Distinguishing Features of Post-Streptococcal GN

Immunofluorescence Pattern in PSGN

Electron Microscopy: Pathognomonic Finding

Histology

Clinical Course in Children

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Feature	PSGN	IgA Nephropathy
IF pattern	IgG/IgM/C3 (granular)	IgA-dominant
EM finding	Subepithelial humps	Mesangial deposits
Trigger	Post-streptococcal	Mucosal infection (IgA1 overproduction)
Prognosis (children)	Excellent	Variable; some progress