Question
Explain the etiopathogenesis, clinical features, morphologic features and complications of Rheumatic heart disease (5+4+4+2)
Answer
Aetiopathogenesis: Rheumatic heart disease (RHD) is a delayed sequela of pharyngitis caused by Group A beta-haemolytic Streptococcus, occurring via a Type II hypersensitivity (molecular mimicry) mechanism: antibodies raised against streptococcal M protein cross-react with structurally similar antigens in human cardiac tissue (myosin, laminin) as well as joints, skin, and brain. This cross-reactive immune response causes tissue injury 2–4 weeks after the initiating streptococcal infection, damaging heart valves and myocardium.
Clinical features: Diagnosed by the revised Jones criteria — evidence of preceding streptococcal infection plus major criteria: migratory polyarthritis, carditis, subcutaneous nodules, erythema marginatum, and Sydenham chorea; minor criteria include fever, arthralgia, elevated ESR/CRP, and prolonged PR interval.
Morphologic features:
- Acute phase: Pancarditis (pericarditis, myocarditis, endocarditis) with Aschoff bodies — foci of fibrinoid necrosis surrounded by lymphocytes, plasma cells, and Anitschkow cells (“caterpillar cells”). Small, warty, non-destructive vegetations along the lines of valve closure (especially mitral valve).
- Chronic phase (chronic RHD): Repeated episodes cause progressive fibrous thickening and fusion of valve leaflets and chordae tendineae, most commonly affecting the mitral valve (mitral stenosis, “fish-mouth” or “buttonhole” deformity), sometimes with the aortic valve also involved.
Complications:
- Mitral stenosis/regurgitation (and less commonly aortic valve disease)
- Infective endocarditis superimposed on damaged valves
- Atrial fibrillation and thromboembolism (from left atrial enlargement/stasis)
- Congestive heart failure
- Recurrent rheumatic fever with cumulative valve damage