Rheumatic fever and rheumatic myocarditis

1. Concept

Rheumatic fever (RF) is an immunologically-mediated, multi-organ acute inflammatory disease following a Group A β-hemolytic Streptococcus pyogenes pharyngitis. The cardiac manifestation is pancarditis (endo-, myo-, and pericardium).

2. Pathogenesis — molecular mimicry

Streptococcal pharyngitis (bacteria stay on tonsils) → streptococcal antigens enter circulation → host antibodies cross-react with glycoproteins of heart, joints, skin, etc. (molecular mimicry) → autoimmune attack → pancarditis, arthritis, vasculitis, glomerulonephritis. It is a type II hypersensitivity-type reaction.

3. Acute rheumatic heart disease

• Aschoff bodies — pathognomonic granulomas: central fibrinoid necrosis surrounded by lymphocytes, plasma cells, and plump activated macrophages = Anitschkow cells (“caterpillar cells”). Found in all 3 layers → pancarditis.
• Endocardium: small verrucae (Ig + fibrin) along valve closure lines.
• Myocardium: Aschoff bodies.
• Pericardium: fibrinous (“bread-and-butter”) pericarditis.
• Other organs: migratory polyarthritis of large joints, post-streptococcal glomerulonephritis, vasculitis.

4. Chronic rheumatic heart disease

• Organization/scarring → leaflet thickening, commissural fusion, thickened/fused chordae tendineae → “fish-mouth” / “button-hole” mitral stenosis (mitral valve most affected).
• Consequences: LA dilation → mural thrombi, RV hypertrophy, high risk of infective endocarditis.

5. Clinical features & diagnosis

• Onset 1–6 weeks after pharyngitis; peak age 5–15 years.
• JONES criteria (need 2 major or 1 major + 2 minor + evidence of strep):
  • Joints (migratory polyarthritis), O = ♥ carditis, Nodules (subcutaneous), Erythema marginatum, Sydenham chorea.
  • Minor: fever, arthralgia, ↑acute-phase reactants.

💡 High-yield: RF = post-strep molecular mimicry → pancarditis. Aschoff bodies + Anitschkow cells are pathognomonic; endocardial verrucae. Chronic → mitral stenosis (“fish-mouth”). Diagnose with JONES criteria (Joints, ♥, Nodules, Erythema marginatum, Sydenham chorea), 1–6 wks post-pharyngitis, age 5–15.