Kawasaki disease is a febrile, exanthematous, multisystem vasculitis of importance, because approximately 20% of untreated children will develop coronary artery abnormalities. Most cases of Kawasaki disease occur in children younger than 12 years of age. The illness is characterized by fever and the following clinical features: (1) bilateral bulbar conjunctival injection without exudate; (2) erythematous mouth and pharynx, strawberry tongue, and red, cracked lips; (3) a polymorphous, generalized, erythematous rash that can be morbilliform, maculopapular, or scarlatiniform or may resemble erythema multiforme; (4) changes in the peripheral extremities consisting of induration of the hands and feet with erythematous palms and soles, often with later periungual desquamation; and (5) acute, nonsuppurative, usually unilateral, cervical lymphadenopathy with at least one node 1.5 cm in diameter. For diagnosis of classic Kawasaki disease, patients should have fever for at least 4 days and at least 4 of these 5 features without alternative explanation for the findings. The epidemiologic case definition also allows diagnosis of Kawasaki disease when a person has fewer than 4 principal clinical criteria in the presence of coronary artery aneurysms. Irritability, abdominal pain, diarrhea, and vomiting commonly are associated features. Other findings include urethritis with sterile pyuria (70% of cases), mild anterior uveitis (25%-50%), mild hepatic dysfunction (40%), arthritis or arthralgia (10%-20%), meningismus with cerebrospinal fluid pleocytosis (25%), pericardial effusion of at least 1 mm (less than 5%), gallbladder hydrops (less than 10%), and myocarditis manifested by congestive heart failure (less than 5%). Fine desquamation in the groin area can occur in the acute phase of disease.¹

Incomplete Kawasaki disease can be diagnosed in febrile patients when fever plus fewer than 4 of the characteristic features are present. Patients with fewer than 4 of the characteristic features and who have additional findings not listed above (eg, purulent conjunctivitis) should not be considered to have incomplete Kawasaki disease. Incomplete Kawasaki disease is more common in infants younger than 12 months of age than in older children. Infants with Kawasaki disease also have a higher risk of developing coronary artery aneurysms than do older children, making diagnosis and timely Treatment especially important in this age group. The laboratory findings of incomplete cases are similar to findings of classic cases. Therefore, although laboratory findings in Kawasaki disease are nonspecific, they may prove useful in increasing or decreasing the likelihood of incomplete Kawasaki disease. If coronary artery ectasia or dilatation is evident, the diagnosis is confirmed. A normal early echocardiographic study does not exclude the diagnosis but may be useful in evaluation of patients with suspected incomplete Kawasaki disease. Incomplete Kawasaki disease should be considered in any child with unexplained fever for 5 days or longer in association with 2 or more of the principal features of this illness and supportive laboratory data (eg, erythrocyte sedimentation rate [ESR] 40 mm/hour or greater or C-reactive protein [CRP] concentration 3.0 mg/dL or greater). Fig 3.2 shows the American Heart Association algorithm for diagnosis and Treatment of suspected incomplete Kawasaki disease.





Without aspirin and Immune Globulin Intravenous (IGIV) therapy, fever can last 2 weeks or longer. After fever resolves, patients can remain anorectic and/or irritable for 2 to 3 weeks. During this phase, desquamation of the groin, fingers, and toes and fine desquamation of other areas may occur. Recurrent disease occurring months to years later develops in approximately 2% of patients.

Coronary artery abnormalities can be demonstrated with 2-dimensional echocardiography in 20% to 25% of patients who are not treated within 10 days of onset of fever. Increased risk of developing coronary artery aneurysms is associated with male sex; age younger than 12 months or older than 8 years; fever for more than 10 days; high baseline neutrophil (greater than 30 000 cells/mm³) and band count; low hemoglobin concentration (less than 10 g/dL); hypoalbuminemia, hyponatremia, or thrombocytopenia at presentation; fever persisting after IGIV administration; and persistence of elevated ESR or CRP for more than 30 days or recurrent elevations. Hispanic ethnicity also has been associated with high risk of coronary artery aneurysms, which may be related to delayed diagnosis and Treatment. Aneurysms of the coronary arteries have been demonstrated by echocardiography as early as 5 to 7 days after onset of illness but more typically occur between 1 and 4 weeks after onset of illness; their initial appearance later than 6 weeks is uncommon. Giant coronary artery aneurysms (diameter 8 mm or greater) are likely to be associated with long-term complications. Aneurysms occurring in other medium-sized arteries (eg, iliac, femoral, renal, and axillary vessels) are uncommon and generally do not occur in the absence of significant coronary abnormalities. In addition to coronary artery disease, carditis can involve the pericardium, myocardium, or endocardium, and mitral or aortic regurgitation or both can develop. Carditis generally resolves when fever resolves.

In children with mild coronary artery dilation or ectasia, coronary artery dimensions often return to baseline within 6 to 8 weeks after onset of disease. Approximately 50% of coronary aneurysms (fewer giant aneurysms) regress to normal luminal size within 1 to 2 years, although this process can be accompanied by development of coronary stenosis. In addition, regression of aneurysm(s) may result in a poorly compliant, fibrotic vessel wall.

The current case-fatality rate in the United States and Japan is less than 0.1% to 0.2%. The principal cause of death is myocardial infarction resulting from coronary artery occlusion attributable to thrombosis or progressive stenosis. Rarely, a large coronary artery aneurysm may rupture. The relative risk of mortality is highest within 6 weeks of onset of symptoms, but myocardial infarction and sudden death can occur months to years after the acute episode. There is hypothetical concern that the vasculitis of Kawasaki disease may predispose to premature coronary artery disease.