## Histopathology of Acute Rheumatic Heart Disease **Key Point:** Aschoff bodies are the **pathognomonic lesion** of acute rheumatic fever (ARF) and acute rheumatic carditis. They are the most characteristic and diagnostically specific finding in the acute phase of RHD. ### Aschoff Body: Definition & Features **High-Yield:** An Aschoff body is a granulomatous lesion composed of: - Central fibrinoid necrosis - Surrounding inflammatory infiltrate (lymphocytes, macrophages, plasma cells) - **Anitschkow cells** (activated macrophages with central wavy ribbon-like chromatin — "caterpillar cells") - **Aschoff giant cells** (multinucleated giant cells formed from Anitschkow cells) ### Temporal Progression of Histopathological Changes | Phase | Timing | Key Lesions | Location | |-------|--------|-------------|----------| | **Acute** | Days to weeks | Aschoff bodies, fibrinoid necrosis, verrucae | Myocardium, valve endocardium | | **Subacute** | Weeks to months | Granulation tissue, early fibrosis | Valve leaflets, myocardium | | **Chronic** | Months to years | Fibrosis, calcification, commissural fusion | Valve | **Clinical Pearl:** Aschoff bodies are found in the **myocardium** during acute carditis, but they are **NOT specific to the heart** — they can also occur in other tissues (pericardium, subcutaneous nodules in acute rheumatic fever). **Mnemonic:** **ABC of ARF histology** — **A**schoff bodies (pathognomonic), **B**ody of lesion (fibrinoid necrosis), **C**ells (Anitschkow + Aschoff giant cells). ### Why Aschoff Bodies Are Most Common in Acute Phase Aschoff bodies represent the **acute inflammatory response** to streptococcal cross-reactivity. They are most abundant in the first 2–3 weeks of acute carditis and gradually resolve as fibrosis takes over. By the chronic phase, they are replaced by scar tissue and calcification.
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