Kawasaki Disease

The etiology of Kawasaki disease is unknown, but the epidemiology and clinical presentation suggest an infection or, more likely, an abnormal immunologic response to an infection in genetically predisposed children. Autoimmune disease is also a possibility.

Children of Japanese descent have a particularly high incidence, but Kawasaki disease occurs worldwide. In the United States, 3000 to 5000 cases occur annually (1). The male:female ratio is about 1.5:1. Eighty percent of patients are < 5 years (peak, 18 to 24 months) of age. Cases in adolescents, adults, and infants < 4 months of age are rare.

Cases occur year-round but most often in spring or winter. Clusters have been reported in communities without clear evidence of person-to-person spread. About 2% of patients have recurrences, typically months to years later. There is no known prevention.

The illness tends to progress in 3 phases: acute, subacute, and convalescent.

The acute phase begins with fever lasting at least 5 days, usually > 39° C (about 102.2° F) and unremittent when not treated with antipyretics. The fever is associated with irritability, occasional lethargy, or intermittent colicky abdominal pain. Usually within a day or two of fever onset, bilateral bulbar conjunctival injection appears without exudate.

Within 5 days, a polymorphous, erythematous, macular rash appears, primarily over the trunk, often with accentuation in the perineal region. The rash may be urticarial, morbilliform, erythema multiforme, or scarlatiniform. It is accompanied by injected pharynx; reddened, dry, fissured lips; and a red strawberry tongue.

Kawasaki Disease (Exanthem)

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This photo shows a polymorphous, erythematous, macular rash over the lower trunk with accentuation in to the perineal region.

© Springer Science+Business Media

Strawberry Tongue (Child)

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This tongue is erythematous with prominent papillation.

SCIENCE PHOTO LIBRARY

During the first week, pallor of the proximal portion of the fingernails or toenails (leukonychia partialis) may occur. Erythema or a purple-red discoloration and variable edema of the palms and soles usually appear on about the 3rd to 5th day. Although edema may be slight, it is often tense, hard, and nonpitting. The acute phase ends with the resolution of fever.

The subacute phase lasts from the end of the fever until about day 25. Periungual, palmar, plantar, and perineal desquamation begins on about day 10. The superficial layer of the skin sometimes comes off in large casts, revealing new normal skin. Arthritis, arthralgia, and thrombocytosis may be present. Arthritis or arthralgias (mainly involving large joints) occur in about 33% of patients.

Cardiac manifestations usually begin in the subacute phase of the syndrome about 1 to 4 weeks after onset as the rash, fever, and other early acute clinical symptoms begin to subside.

Tender, nonsuppurative cervical lymphadenopathy (≥ 1 node ≥ 1.5 cm in diameter) is present throughout the course in about 50% of patients. The illness may last from 2 to 12 weeks or longer. Incomplete or atypical cases can occur, especially in younger infants, who have higher risk of developing coronary artery disease. These findings manifest in about 90% of patients.

Other less specific findings indicate involvement of many systems.

Other clinical features may include urethritis, aseptic meningitis, hepatitis, otitis, vomiting, diarrhea, hydrops of the gallbladder, upper respiratory symptoms, and anterior uveitis.

The convalescent phase begins when clinical signs disappear and continues until about 6 to 8 weeks after the onset of the acute phase.

• Clinical criteria (fever ≥ 5 days and characteristic physical examination findings)

• Serial ECG and echocardiography

Diagnosis of Kawasaki disease is by clinical criteria (see table Criteria for Diagnosis of Kawasaki Disease).

Similar symptoms can result from scarlet fever, staphylococcal exfoliative syndromes, measles, drug reactions, and juvenile idiopathic arthritis. Less common mimics are leptospirosis and Rocky Mountain spotted fever.

A postinfectious inflammatory syndrome called multisystem inflammatory syndrome in children (MIS-C) has been observed as a rare complication of SARS-CoV-2 infection. Symptoms of MIS-C are similar to those of Kawasaki disease. Similarities include shock, erythematous rash, conjunctivitis, mucous membrane involvement, lymphadenopathy, and cardiac changes. However, children with MIS-C should have serologic evidence of COVID-19 infection and they tend to present with more gastrointestinal (diarrhea and vomiting) and neurologic (headache) symptoms than do children with Kawasaki disease. Additionally, children with Kawasaki disease tend to have limbic-sparing conjunctivitis and are younger (typically under 5 years of age) (1, 2).

Some febrile children who have fewer than 4 of the 5 diagnostic criteria nonetheless develop vasculitic complications, including coronary artery aneurysms. Such children are considered to have atypical (or incomplete) Kawasaki disease. Atypical Kawasaki disease should be considered, and testing should be initiated if the child has had ≥ 5 days of fever > 39° C (about 102.2° F) plus ≥ 2 of the 5 criteria for Kawasaki disease.

Laboratory tests are not diagnostic but may be done to exclude other disorders. Patients generally undergo complete blood count, antinuclear antibody, rheumatoid factor, erythrocyte sedimentation rate (ESR), and throat and blood cultures.

Leukocytosis, often with a marked increase in immature cells, is common acutely. Other hematologic findings include a mild normocytic anemia, thrombocytosis (≥ 450,000/mcL [≥ 450 × 10⁹/L]) in the second or third week of illness, and elevated ESR or C-reactive protein. Antinuclear antibody, rheumatoid factor, and cultures are negative.

Consultation with a pediatric cardiologist is important. At diagnosis, ECG and echocardiography are done. Because abnormalities may not appear until later, these tests are repeated 2 to 3 weeks, 6 to 8 weeks, and perhaps 6 to 12 months after onset. ECG may show arrhythmias, decreased voltage, or left ventricular hypertrophy. Echocardiography should detect coronary artery aneurysms, valvular regurgitation, pericarditis, or myocarditis. Coronary arteriography occasionally is useful in patients with aneurysms and abnormal stress test results.

• High-dose IV immune globulin (IVIG)

• High-dose aspirin

Children should be treated by or in close consultation with an experienced pediatric cardiologist, pediatric infectious disease specialist, or pediatric rheumatologist.

aspirin therapy when begun > 10 days after onset of illness is unknown, but therapy should still be considered.

The aspirin dose is reduced to 3 to 5 mg/kg once a day after the child has been afebrile for 4 to 5 days; some authorities prefer to continue high-dose aspirin until the 14th day of illness. Aspirin metabolism is erratic during acute Kawasaki disease, which partially explains the high dose requirements. Some authorities monitor serum aspirin levels during high-dose therapy, especially if therapy is given for 14 days and/or fever persists despite IVIG treatment.

Most patients have a brisk response over the first 24 hours of therapy. A small fraction continue to be ill with fever for several days and require repeated dosing with IVIG. Treatment of refractory disease should be conducted with input from a cardiologist and rheumatologist.

An alternative regimen may benefit patients with cardiac dysfunction who could not tolerate the volume of a 2 g/kg IGIV infusion but may lead to slightly slower resolution of symptoms. The alternative regimen is IVIG 400 mg/kg once a day for 4 days (again in combination with high-dose aspirin).

aspirin may be stopped. Because of its antithrombotic effect, aspirin

With adequate therapy, mortality in the United States is 0.17%. Long duration of fever increases cardiac risk.

Deaths most commonly result from cardiac complications and can be sudden and unpredictable: > 50% occur within 1 month of onset, 75% within 2 months, and 95% within 6 months but may occur as long as 10 years later. Effective therapy reduces acute symptoms and, more importantly, lowers the incidence of coronary artery aneurysms from 20% to < 5%.

In the absence of coronary artery disease, the prognosis for complete recovery is excellent. About two thirds of coronary aneurysms regress within 1 year, although it is unknown whether residual coronary stenosis remains. Giant coronary aneurysms are less likely to regress and require more intensive follow-up and therapy.