Rheumatic Fever: Pathology and Causes

Study Notes

Definition: Autoimmune collagen disease affecting the heart and joints of children and young adults
Predisposing factors:
- Age: 5-15 years
- Low socio-economic standards and overcrowding, leading to malnutrition and recurrent streptococcal infections (e.g., tonsillitis)
- Personal susceptibility (genetic factor)
Aetiology and pathogenesis:
- Acute upper respiratory tract infection (e.g., tonsillitis) caused by streptococci
- Latent period of 2-4 weeks, during which antibodies against streptococcal antigens are formed
- Antibodies destroy collagen in tissues through:
  - Type II hypersensitivity reaction via cross-reaction
  - Type III hypersensitivity reaction via Ag-Ab complexes
  - Type IV hypersensitivity reaction via Aschoff body formation
Pathology:
- Aschoff bodies (nodules) in the heart, skin, and other tissues
- Aschoff bodies are composed of:
  - Central zone of fibrinoid necrosis (fragmented collagen)
  - Surrounding lymphocytes and Aschoff's giant cells
- Fate of Aschoff bodies: Fibrosis

Heart:
- Rheumatic pan-carditis (affecting all layers of the heart)
- Aschoff nodules leading to fibrosis
- Endocarditis (affecting the inner walls of the left atrium, valves, and leading to valve stenosis and incompetence)
- Myocarditis
- Pericarditis (serofibrinous inflammation)
Joints and tendons:
- Fleeting (migratory) arthritis of large joints
Skin:
- Subcutaneous nodules over bony prominences
Brain:
- Reversible involuntary movements (Chorea minor) due to inflammation of the basal ganglia
Pleura and peritoneum:
- Serofibrinous inflammation
Large arteries:
- Affected by Aschoff's nodules

Sub-acute infective endocarditis
Heart failure due to repeated attacks of myocarditis and valve stenosis or incompetence
Adhesion of pericardium, leading to impaired cardiac action

Definition: Disease of the myocardium due to insufficient coronary blood flow
Acute Ischemia:
- Sudden complete occlusion of coronary artery
- Caused by atheroma, thrombosis, rupture of the plaque, and hemorrhage into the plaque
- Leads to myocardial infarction
Chronic Ischemia:
- Gradual incomplete occlusion of coronary artery
- Caused by atheroma, anemia, increased cardiac load, and ventricular hypertrophy
- Leads to angina pectoris mainly

Definition: Clinical syndrome characterized by temporary acute attacks of severe retro-sternal pain
Causes:
- Temporary acute ischemia on top of chronic ischemia
- Decreased coronary arterial blood flow
Clinical Presentation:
- Precipitated by physical exercise, heavy meals, anxiety, or cold
- Pain is stabbing in nature, referred to the left shoulder and left arm
- Relieved by rest
Prognosis (complications):
- May be fatal due to ventricular fibrillation, myocardial infarction, or heart failure

Definition: Massive area of coagulative necrosis of myocardium due to sudden complete stoppage of coronary arterial blood supply
Aetiology:
- Decreased coronary arterial blood flow due to acute ischemia
Effects of occlusion:
- Depends on the size of the occluded artery and collateral circulation
- May lead to sudden death, infarction, or survival with good collaterals
Sites of infarction:
- Correspond to the distribution of the occluded artery
- Commonly involves the left ventricle
Morphology of the infarct area:
- Varies with duration of infarction
- Initially, no morphological changes
- Then, coagulative necrosis, softening of the myocardium, and infiltration by neutrophils
- Eventually, fibrous scar develops with thinning of the ventricular wall