Which of the following is the hallmark immunofluorescence pattern in post-streptococcal glomerulonephritis (PSGN)?

Explanation

## Immunofluorescence Pattern in PSGN **Key Point:** Post-streptococcal glomerulonephritis (PSGN) is characterized by a **granular pattern of IgG and C3 deposition** on immunofluorescence microscopy, often described as a "starry sky" or "lumpy-bumpy" appearance. ### Pathophysiology PSGN is an immune complex-mediated glomerulonephritis that develops 1–3 weeks after a Group A Streptococcal (GAS) infection (pharyngitis or impetigo). The immune complexes deposit in the glomeruli, activating complement via the classical pathway. ### Light Microscopy Findings - Diffuse proliferative glomerulonephritis - Hypercellularity (endocapillary proliferation) - Crescent formation (in severe cases) - Subepithelial "humps" on electron microscopy (pathognomonic) ### Immunofluorescence Pattern | Feature | Finding | |---------|----------| | **IgG** | Granular deposition | | **C3** | Granular deposition (often more prominent than IgG) | | **Pattern** | "Starry sky" or "lumpy-bumpy" | | **Location** | Subepithelial, subendothelial, and mesangial | **High-Yield:** The **granular C3-dominant pattern** is the most characteristic finding and helps distinguish PSGN from other forms of acute glomerulonephritis. ### Clinical Correlation - Presents with hematuria, proteinuria, hypertension, and edema - Most cases resolve spontaneously in children; adults may have residual renal dysfunction - Prognosis is generally favorable with supportive care