Pathogenesis of Kawasaki disease.

Kawasaki disease (KD) most frequently affects infants and young children under 5 years of age. This disease is considered a kind of systemic vasculitis syndrome, and primarily invades the medium-sized muscular arteries, including coronary arteries. Diagnosis of KD is based on characteristic clinical signs and symptoms, which are classified as principal clinical findings and other clinical and laboratory findings. Even though the aetiology of KD is unknown, epidemiological data suggest that some kinds of infectious agents are involved in the onset of KD. In addition, the data indicate that host genetics underlie the disease's pathogenesis. Histologically, coronary arteritis begins 6-8 days after the onset of KD, and leads immediately to inflammation of all layers of the artery. The inflammation spreads completely around the artery; as a result, structural components of the artery undergo intense damage; the artery then begins to dilate. Inflammatory cell infiltration continues until about the 25th day of the disease, after which the inflammatory cells gradually decrease in number. KD arteritis is characterized by granulomatous inflammation that consists of severe accumulation of monocytes/macrophages. Aberrant activation of monocytes/macrophages is thought to be involved in the formation of vascular lesions. The lesions in all the arteries are relatively synchronous as they evolve from acute to chronic injury. There is no fibrinoid necrosis nor any mixture of acute inflammatory lesions and scarring lesions, which are characteristics in polyarteritis nodosa in KD.