Aschoff body
Aschoff body
An Aschoff body (also called Aschoff nodule) is the pathognomonic lesion of rheumatic heart disease (RHD).
Key Features:
- Definition:
A localized, inflammatory lesion found in the myocardium during rheumatic fever. - Histology:
- Central fibrinoid necrosis (degeneration of collagen and connective tissue).
- Surrounded by Aschoff (anitschkow) cells → large macrophages with abundant cytoplasm and characteristic “caterpillar nuclei” (long, wavy chromatin).
- Also contains lymphocytes, plasma cells, and multinucleated giant cells.
- Location:
- Typically in the interstitial connective tissue of the myocardium.
- May also occur in the endocardium and pericardium.
- Pathogenesis:
- Results from an autoimmune response (molecular mimicry between streptococcal antigens and cardiac myosin/connective tissue).
- Clinical relevance:
- Seen in acute rheumatic fever (especially myocarditis stage).
- Healing of Aschoff bodies leads to fibrous scar tissue → contributes to chronic valvular deformities (especially mitral stenosis).
🔑 Exam tip:
- Aschoff body = pathognomonic lesion of rheumatic carditis.
- Anitschkow cells = activated macrophages within Aschoff bodies, nuclei look like caterpillars (slender, wavy chromatin).
Aschoff Body — 20 MCQs
Location and composition
- Location: Aschoff bodies are most frequently found in the myocardium (the heart muscle) and endocardium, particularly in the walls of the left atrium and ventricle. They are especially common in the connective tissue near small blood vessels.
- Composition: A fully developed Aschoff body is a granuloma, a small area of inflammation. It contains:
- Fibrinoid necrosis: A central area of degenerated collagen and other protein material.
- Inflammatory cells: An infiltration of immune cells, including T-lymphocytes, plasma cells, and macrophages.
- Characteristic cells: Two specific types of large cells are found within Aschoff bodies:
- Anitschkow cells: Also called "caterpillar cells," these are activated macrophages with a unique, wavy-looking chromatin pattern in their nuclei.
- Aschoff giant cells: These are multinucleated macrophages formed by the fusion of Anitschkow cells.
Developmental stages
Aschoff bodies evolve through three stages, which can all be present in the heart at the same time during an acute infection:
- Exudative/Degenerative stage: The earliest phase, marked by swelling of the connective tissue and an increase in acid mucopolysaccharides, leading to the breakdown of collagen fibers.
- Proliferative/Granulomatous stage: In this phase, the fibrinoid core is surrounded by characteristic inflammatory cells, including Anitschkow cells, forming the classic granulomatous Aschoff body.
- Fibrous/Healing stage: The nodules become less cellular and are eventually replaced by fibrous, collagenous scar tissue. The resulting scars can cause permanent damage, especially to the heart valves.
Clinical significance
- Diagnosis: Aschoff bodies are crucial for confirming a diagnosis of rheumatic heart disease. Their presence indicates that the patient experienced an episode of acute rheumatic carditis (inflammation of the heart).
- Sequelae: The scarring that results from the healing of Aschoff bodies can lead to long-term cardiac complications, most notably thickening and fusion of heart valves. This can cause valvular stenosis (narrowing) or regurgitation (leakage) years after the initial illness. The mitral valve is most frequently affected.
- Autoimmune origin: The formation of Aschoff bodies is part of an autoimmune response, where antibodies created to fight the strep infection mistakenly attack the heart's connective tissue.
