Ultrastructural characteristics of myocardial and coronary microvascular lesions in Kawasaki disease.

Kawasaki disease (KD) is an acute febrile mucocutaneous lymph node syndrome with multisystemic vasculitis affecting mainly infants and children. Although several studies on cardiovascular lesions in KD have been done at the light microscopic level, the ultrastructural characteristics and incidences of these lesions have not been well defined. In order to investigate the myocardial and coronary microvascular sequelae in KD, we performed an ultrastructural study on endomyocardial biopsy specimens obtained during follow-up from 54 patients who had typical clinical manifestations of KD, of whom 47 had associated coronary aneurysms as demonstrated by coronary arteriography (CAG) or two-dimensional echocardiography in the acute or healed stage. The average age of onset was 2.2 years old and the duration of illness was from 2 months to 23 years. Follow-up CAG showed that the coronary aneurysms persisted in 33 of the 47 patients (8 with associated stenosis) and resolved in the remaining 14 patients. Ultrastructurally, the myocardial changes revealed hypertrophy, various degrees of degeneration, proliferation and abnormality of mitochondria, infiltration of a small number of lymphocytes, and fibrosis. The coronary microvascular lesion was characterized by microvascular dilatation, endothelial cell injury, platelet aggregation with thrombosis, and stenotic lumen with thickened walls in the small arterioles. It persisted after convalescent stage even up to 23 years and closely correlated with the myocardial sequelae. Moreover, significantly increased incidences of myocardial and coronary microvascular lesions were found in patients with coronary artery lesion. These findings suggest the coronary microvascular lesion as a possible underlying factor of persistent sequelae in KD.