Understanding Rheumatic Fever: Causes, Symptoms, and Complications
Classified in Biology
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Rheumatic Fever
Is a multisystem inflammatory disease that can involve the heart, joints, skin, and brain. The disease develops after a streptococcal infection (A beta-hemolytic – Streptococcus pyogenes) – mostly pharyngitis
Clinical Features
- Occur most often in children
- Develop 2-4 weeks after streptococcal infection
- Fever, malaise, and increased erythrocyte sedimentation rate
- Rheumatic heart disease – pancarditis; inflammation of the entire heart (3 layers)
Pericarditis
Leads to serous effusions
Myocarditis
Leads to cardiac failure
Endocarditis
Leads to valvular damage
- Rheumatic endocarditis – mitral and aortic valves (mostly); the valves become thickened, fibrotic, deformed, & calcification (may)
- Joint involvement – arthralgia, arthritis, and migratory polyarthritis
- Skin lesions – subcutaneous nodules and erythema marginatum (distinctive)
- CNS involvement – Sydenham chorea (involuntary muscular movements)
- If chronic – arrhythmias and thromboembolic complications
Causes
- Immunologic origin rather than a result of direct bacterial involvement
- Streptococcal antigens – molecular mimicry – elicit an antibody cross-reactivity
Mechanism
- Type II hypersensitivity – attributed to antibodies against group A streptococcal molecules that cross-react with host myocardial antigens
Morphology
Acute Rheumatic Fever
- Inflammation foci within several tissues
- Aschoff bodies – focal interstitial myocardial inflammation, with:
- Aschoff cells – multinucleated giant cells
- Anitschkow myocytes or “caterpillar cells”
- Collagen and fibrinoid material
- Aschoff bodies can be found in all three layers of the heart
- The pericardium exhibits fibrinous exudate
- The endocardium may contain verrucae (1-2mm vegetations)
Chronic Rheumatic Fever
- Organization of acute diffuse inflammation and scarring
- Aschoff bodies are replaced by fibrous scar – therefore not seen in chronic RF
- Cardiac valves show leaflet thickening, commissural fusion and shortening, and thickening of the chordae tendinea
- Calcification creates buttonhole stenoses
- Neovascularization
Rheumatic Heart Disease
- Valvular stenosis and regurgitation
- 70% mitral valve
- 25% mitral and aortic valves
- 5% tricuspid valve
- Mitral valve stenosis à left atrium dilation à atrial fibrillation à mural thrombosis