Key Concepts
Introduction
Kawasaki disease (KD) is an acute systemic vasculitis of unknown etiology that predominantly affects children under 5 years of age. It is the leading cause of acquired heart disease in children in developed countries. The disease targets medium-sized muscular arteries, with a particular tropism for the coronary arteries. The pathogenesis involves a dysregulated immune response triggered by an unknown agent (likely infectious) in genetically susceptible children. The inflammatory process progresses through three pathological phases in the coronary arteries: (1) acute necrotizing arteritis (first 2 weeks) with neutrophilic infiltration of the arterial wall destroying the intima, media, and internal elastic lamina; (2) subacute/chronic vasculitis (weeks 2-8) with lymphocytic and plasma cell infiltration causing progressive arterial wall weakening; and (3) luminal myofibroblastic proliferation (months to years) where intimal thickening can cause stenosis. Coronary artery aneurysms develop in 15-25% of untreated children, most commonly in the proximal left anterior descending (LAD) and right coronary artery (RCA). Aneurysm formation occurs because inflammation destroys the structural integrity of the arterial wall (particularly the media and elastic lamina), allowing the vessel to dilate under arterial pressure....