In Kawasaki disease, a form of medium-vessel vasculitis predominantly affecting coronary arteries in children, the pathological sequence leading to coronary aneurysm formation involves:

• A Immune complex deposition in coronary artery walls activating complement and causing Type III hypersensitivity vasculitis
• B T-cell-mediated granulomatous destruction of the IEL identical to giant cell arteritis
• C Neutrophil and macrophage-mediated destruction of the media with matrix metalloproteinase (MMP) release causing elastic fibre fragmentation and aneurysmal dilatation ✓
• D ANCA-mediated neutrophil activation causing fibrinoid necrosis of coronary artery walls

Explanation

In Kawasaki disease, the acute phase shows intense neutrophilic infiltration of all three coronary artery wall layers. Neutrophils and subsequently macrophages release matrix metalloproteinases (particularly MMP-9, MMP-12) and reactive oxygen species that degrade elastin and collagen in the media. Destruction of the medial elastic and smooth muscle components leads to weakening of the vessel wall and coronary artery aneurysm formation (most feared complication). CD8+ cytotoxic T cells and macrophages also contribute. The initiating stimulus remains unknown (suspected infectious trigger in genetically susceptible Asian children). Intravenous immunoglobulin (IVIG) within first 10 days reduces coronary aneurysm risk. Immune complex (Type III) vasculitis is not the mechanism; ANCA vasculitis affects small vessels; GCA is a different granulomatous vasculitis.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.