Rheumatic Fever: Strep Trigger, Autoimmune Mechanism, and Prevention

Pathogenesis

Group A Streptococcus (GAS) infection → molecular mimicry → autoimmune attack on heart, joints, brain, skin.

Precipitating Infections

• Strep throat (pharyngitis)
• Scarlet fever
• Impetigo (skin infection)

Autoimmune Mechanism

Antibodies to streptococcal M protein cross-react with host tissues: cardiac myosin (heart), joint synovium, basal ganglia (brain), skin.

Risk Factors

• Age: 5–15 years peak incidence.
• Genetics: HLA associations, family history.
• Environment: Crowding, poverty, malnutrition.
• Strain virulence: Certain M types more rheumatogenic.

Diagnosis: Modified Jones Criteria

• Major criteria: Carditis, polyarthritis, Sydenham chorea, erythema marginatum, subcutaneous nodules.
• Minor criteria: Fever, arthralgia, elevated acute phase reactants (ESR/CRP), prolonged PR interval.
• Required: 2 major OR 1 major + 2 minor + evidence of recent GAS infection.

Prevention

Prompt penicillin treatment of GAS pharyngitis prevents rheumatic fever. Secondary prophylaxis (long-term penicillin) for those with prior rheumatic fever.