Rheumatic Heart Disease (RHD) - Pathology with Images

1. Overview

2. Pathogenesis - Molecular Mimicry

• Antibodies against streptococcal M proteins also recognize cardiac myosin, laminin, and tropomyosin in the myocardium and valves
• These cross-reactive antibodies bind valvular endothelium, upregulating adhesion molecules (VCAM-1, ICAM-1) that facilitate CD4+ T cell infiltration into the valve
• Cytokines from T cells drive macrophage activation, forming Aschoff bodies
• The characteristic 2-3 week delay in symptom onset after infection reflects the time needed to generate this immune response - by this point, no live streptococci remain in the lesions
• Only ~1-3% of infected patients develop ARF, suggesting genetic susceptibility

3. Acute Rheumatic Fever - Pancarditis

Pericarditis

• Fibrinous exudate on pericardium
• Usually resolves without sequelae ("bread-and-butter" pericarditis)

Myocarditis - Aschoff Bodies

• Collections of lymphocytes (mostly T cells), scattered plasma cells, and plump activated macrophages called Anitschkow cells (caterpillar cells)
• Anitschkow cells have abundant cytoplasm with nuclei showing centrally condensed chromatin in a wavy ribbon pattern - the "caterpillar nucleus"
• Zones of fibrinoid necrosis surround the cellular infiltrate
• Found in the interstitial connective tissue of the myocardium

Aschoff body in acute rheumatic myocarditis: mixed mononuclear inflammatory infiltrate including large Anitschkow macrophages with characteristic caterpillar chromatin (H&E) - Sherris & Ryan's Medical Microbiology

Endocarditis / Valvulitis (Acute)

• Fibrinoid necrosis along the valve leaflet closure lines
• Formation of small 1-2 mm vegetations called verrucae along the lines of leaflet closure
• These vegetations cause little hemodynamic disturbance acutely

4. Gross and Microscopic Pathology - Key Images

FIG. 9.19 (Robbins & Kumar Basic Pathology):

• (A) Acute rheumatic mitral valvulitis superimposed on chronic RHD - small verrucous vegetations visible along the line of leaflet closure (arrows); chordae tendineae already fibrous and fused from previous episodes
• (B) Microscopic Aschoff body - activated macrophages (Anitschkow cells) with prominent nucleoli and central wavy "caterpillar" chromatin (arrows)
• (C) Chronic mitral stenosis viewed from above - diffuse fibrous thickening, commissural fusion (arrows), and marked left atrial dilation
• (D) Anterior leaflet of rheumatic mitral valve showing neovascularization (arrow) - a hallmark of chronic inflammation/healing
• (E) Rheumatic aortic stenosis specimen - thickening and distortion of cusps

5. Chronic Rheumatic Heart Disease

The "Fish Mouth" / "Buttonhole" Valve

FIGURE 112.12 (Sabiston Textbook of Surgery): Classic pathognomonic "fish mouth" funnel valve deformity of chronic rheumatic mitral valve disease. Fusion and shortening of the leaflets at the commissures severely narrows the valve orifice. This mixed stenotic/regurgitant pattern is the end result of repeated valvulitis episodes.

6. Valves Affected - Order of Frequency

7. Consequences of Chronic RHD

1. Left atrial dilation due to pressure overload from obstructed inflow
2. Atrial fibrillation from atrial dilation and fibrosis
3. Left atrial mural thrombus - from AF + dilation (risk of systemic embolism and stroke)
4. Pulmonary hypertension from passive venous congestion
5. Right ventricular hypertrophy and eventual failure
6. Left ventricle is typically normal in pure mitral stenosis

8. Summary Diagram of Pathologic Progression

Group A Strep pharyngitis
         ↓
Molecular mimicry (M-protein vs. cardiac myosin/laminin)
         ↓
ACUTE RHEUMATIC FEVER (2-3 weeks later)
         ↓
PANCARDITIS
  ├── Pericarditis (fibrinous, usually resolves)
  ├── Myocarditis (Aschoff bodies + Anitschkow cells)
  └── Valvulitis (verrucae on line of closure)
         ↓ (repeated attacks → progressive scarring)
CHRONIC RHD
  ├── Leaflet fibrosis and thickening
  ├── Commissural fusion → stenosis
  ├── Chordal fusion and shortening
  └── "Fish mouth" mitral valve
         ↓
COMPLICATIONS
  ├── LA dilation → AF → thrombus → embolism
  ├── Pulmonary hypertension
  └── Right heart failure