Serpiginous/snake-like erythematous rash with central clearing on trunk
Pathognomonic for acute rheumatic fever
Jones Criteria (major): Joints (migratory polyarthritis), ♥ carditis, Chorea (Sydenham's), Erythema marginatum, Subcutaneous nodules
Preceded by Group A Strep pharyngitis (not skin infection)
Mechanism: molecular mimicry → antibodies cross-react with cardiac tissue
Most serious complication: mitral stenosis (years later)
Tx: penicillin + aspirin; long-term prophylaxis to prevent recurrence