Pathophysiology

The pathogenesis of Kawasaki disease is poorly understood.  The leading theory is that an unknown stimulus triggers an immune-mediated inflammatory cascade in a genetically susceptible child causing damage to the small and medium sized vessels the most clinically significant of which are the coronary vessels^3-5.

The coronary artery is composed of three layers:

1. Tunica intima single layer of endothelial cells.
2. Tunica media thicker layer of smooth muscle cells.
3. Tunica adventitia surrounding layer of loose connective tissue.

In Kawasaki disease, neutrophilic infiltration occurs in the first two weeks causing destruction of the intima, media and adventitia. This leads to aneurysm formation and necrotising arteritis; a common histopathological finding observed in vasculitic disease processes (Figure 1). Pro-inflammatory mediators also promote thrombosis formation and stenosis of arteries (Figure 2).

Figure 1. Inflammatory mediators cause inflammation and destruction of the coronary arteries⁶

Figure 2. Epicardial coronary artery (right) and epicardial vein (left) from a 19-month-old child who died 10 months after Kawasaki disease onset. The epicardial vein contains blood and shows mild thickening of the wall, while the coronary artery shows almost complete occlusion by luminal myofibroblastic proliferation with a fine slit-like lumen³.