Which histopathological lesion is pathognomonic for acute rheumatic carditis and is characterized by central fibrinoid necrosis surrounded by lymphocytes, plasma cells, and Anitschkow cells?

Explanation

## Aschoff Body: The Hallmark of Acute Rheumatic Carditis **Key Point:** The Aschoff body is the pathognomonic histological lesion of acute rheumatic carditis. It is a granulomatous lesion found in the myocardium, endocardium, and pericardium. ### Microscopic Architecture of an Aschoff Body | Component | Cell Type | Function | |-----------|-----------|----------| | **Central core** | Fibrinoid necrosis | Immune-mediated damage | | **Inner layer** | Anitschkow cells (activated macrophages) | Phagocytosis of necrotic debris | | **Outer layer** | Lymphocytes, plasma cells, fibroblasts | Chronic inflammatory response | | **Occasional cells** | Aschoff giant cells (multinucleated) | Fusion of Anitschkow cells | **High-Yield:** Anitschkow cells are pathognomonic for ARF. They are activated macrophages with a characteristic "caterpillar" or "wavy ribbon" appearance of the nucleus due to wavy chromatin. ### Timeline of Aschoff Body Evolution 1. **Acute phase** (weeks 1–2): Central fibrinoid necrosis, dense inflammatory infiltrate 2. **Healing phase** (weeks 2–8): Fibroblasts proliferate, necrosis resolves 3. **Healed phase** (months): Replaced by fibrous scar with hyalinization **Clinical Pearl:** Aschoff bodies are found in all three layers of the heart (pancarditis), but are most common in the myocardium. Their presence confirms acute rheumatic carditis histologically. **Mnemonic: ASCHOFF** — Anitschkow cells + Stratum of lymphocytes + Central fibrinoid necrosis + Hyalinization → Organized fibrous scar (in healing)