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Kawasaki disease (KD), the leading cause of acquired heart disease in children in developed nations, is a multisystem inflammatory illness that particularly affects blood vessels, especially the coronary arteries. About 25% of untreated children develop coronary artery abnormalities, including dilatation and aneurysms that can lead to myocardial infarction and sudden death.1,2 The etiology is unknown, but clinical and epidemiologic data support an infectious cause. In KD, an intense inflammatory cell response develops in a wide array of organs and tissues3; in medium-sized arteries such as the coronary arteries, this response can damage collagen and elastin fibers in the vessel walls and lead to loss of their normal structural integrity with resultant ballooning or aneurysm formation. Despite a limited understanding of KD pathogenesis, a very effective therapy exists in the form of IVIG and aspirin; when given in the first 10 days of fever, this therapy reduces the prevalence of coronary artery abnormalities from 25% in untreated patients to 5% in those who receive the therapy.4 Because the etiology is unknown, no diagnostic test exists, and the diagnosis is made clinically. Classic KD is diagnosed in a patient with prolonged fever and four of five other clinical findings (Box 167-1). However, incomplete forms of illness are well-recognized, in which a child manifests prolonged fever with fewer than four other clinical features of the illness and subsequently develops coronary artery abnormalities. The existence of these incomplete forms of illness results in a major diagnostic dilemma for physicians in establishing the diagnosis accurately in children with prolonged fever of uncertain cause.
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