Pathology of the heart in Kawasaki disease.

Pathologic studies were done on 20 hearts of patients who had typical clinical signs and symptoms of Kawasaki disease. The cardiac lesions were classified according to the duration of illness at the time of death. Stage I (zero to nine days) was characterized by acute perivasculitis and vasculitis of the microvessels (arterioles, capillaries, and venules) and small arteries, and acute perivasculitis and endarteritis of the three major coronary arteries (MCAs). Pericarditis, myocarditis, inflammation of the atrioventricular conduction system, and endocarditis with valvulitis were also present. Stage II (12 to 25 days) was characterized by panvasculitis of the MCAs and aneurysm with thrombus in the stems. Myocarditis, coagulation necrosis, lesion of the conduction system, pericarditis, and endocarditis with valvulitis were also present. In stage III (28 to 31 days), granulation of the MCAs and disappearance of inflammation in the microvessels were noted. Patients in stage IV (40 days to 4 years) had scarring with severe stenosis in the MCAs. Fibrosis of the myocardium, coagulation necrosis, lesions of the conduction system, and endocardial fibroelastosis were also present. The features observed revealed Kawasaki disease to be acute and inflammatory. The angiitis begins in the microvessels and fibrinoid necrosis of the media is rare. The disease is one with a pathologic pattern previously unknown.