Coronary artery aneurysms develop in weanling rabbits with serum sickness but not in mature rabbits. An experimental model for Kawasaki disease in humans.

The involvement of the cardiovascular system in rabbits with serum sickness is similar of that in Kawasaki disease, both with respect to the histologic changes of the myocardium, the valves, the coronary arteries, and the aorta and to the sequence with which they appear. Although coronary arteritis appears the same histologically, aneurysms did not occur in mature rabbits, even in case of necrosis of an arterial segment with deletion of muscle and elastic tissue. On the other hand, weanling rabbits with serum sickness had a tendency to develop aneurysms of coronary arteries, despite little cellular infiltration and reactive fibrocellular hyperplasia. The age factor thus appears to play an important role in the development of coronary aneurysms in Kawasaki disease, irrespective of the underlying mechanism, be it a markedly increased permeability to mediators through degenerated endothelial cells, or primary degenerated muscle cells with marked thinning of the media without much inflammatory cellular reaction. Furthermore, this study provides an insight into the long-term prognosis of transient dilatation of coronary arteries in the acute stage of Kawasaki disease.