Rheumatic Fever - Acute

Definition

Acute rheumatic fever (ARF) is a systemic inflammatory disease that occurs as a delayed, autoimmune response to a Group A Streptococcus (GAS) pharyngeal infection, primarily affecting the heart, joints, skin, and central nervous system in children.

Epidemiology

• Common in children aged 5–15 years
• Higher incidence in low- and middle-income countries
• Peak occurrence 2–4 weeks after untreated or inadequately treated streptococcal pharyngitis
• Incidence declining in developed countries due to antibiotics and better hygiene
• More common in children with repeated GAS infections and in crowded living conditions

Etiology

• Preceding infection with Group A beta-hemolytic Streptococcus (Streptococcus pyogenes)
• Host genetic susceptibility influencing autoimmune response
• Repeated or untreated GAS pharyngitis increases risk
• Immune-mediated molecular mimicry between streptococcal antigens and human tissues

Pathophysiology

• Cross-reactive antibodies and T cells target host tissues (heart, joints, CNS, skin) due to molecular mimicry
• Inflammation of endocardium, myocardium, and pericardium leads to carditis
• Polyarthritis results from immune complex deposition in synovial tissue
• Subcutaneous nodules and erythema marginatum due to vascular inflammation
• Sydenham chorea results from antibody-mediated effects on basal ganglia neurons
• Persistent inflammation may lead to chronic rheumatic heart disease