The cause of Kawasaki disease is unknown but may be associated with an infection.
Children typically have fever, rash, and a red strawberry tongue, and some develop heart complications that rarely can be fatal.
The diagnosis is based on established criteria.
With prompt treatment, nearly all children recover.
Children are given high doses of immune globulin and aspirin.
Kawasaki disease causes inflammation in the walls of blood vessels (vasculitis) throughout the body. The cause of Kawasaki disease is unknown, but evidence suggests a virus or other infectious organism triggers an abnormal immune system response in genetically predisposed children. Inflammation of blood vessels in the heart causes the most serious problems. The inflammation also can spread to other parts of the body such as the pancreas and kidneys.
Most children with Kawasaki disease range in age from 1 to 8 years, although infants and adolescents can be affected. Roughly one and one half times as many boys as girls are affected. The illness is more common among children of Japanese descent. Several thousand cases of Kawasaki disease are estimated to occur in the United States every year. Kawasaki disease occurs year-round but most often in spring or winter.
The illness begins with fever that is usually above 102.2° F (39° C) and that rises and falls over 1 to 3 weeks. The child's temperature does not return to normal unless drugs that lower the temperature (such as acetaminophen and ibuprofen) are given. Within a day or two, the eyes become red but do not have any discharge. Within 5 days, a red, often patchy rash usually appears over the trunk, around the diaper area, and on mucous membranes, such as the lining of the mouth or vagina. The rash may look like hives or may look like the rash caused by measles or scarlet fever. The child has a red throat; reddened, dry, cracked lips; and a red tongue that looks somewhat like a strawberry. Also, the palms and soles turn red or purplish red, and the hands and feet often swell. The skin on the fingers and toes begins to peel about 10 days after the illness starts. The lymph nodes in the neck are often swollen and slightly tender. The illness may last from 2 to 12 weeks or longer.
If children are not treated, up to 1 in 4 develop heart problems, usually beginning 1 to 4 weeks after the illness starts. A few of these children develop the most serious heart problem, a bulge in the wall of a coronary artery (coronary artery aneurysm). These aneurysms can rupture or provoke a blood clot, leading to a heart attack and sudden death. Treatment reduces the risk of heart complications to about 1 in 20.
Other problems include painful inflammation of the tissues lining the brain (meningitis), ears, eyes, liver, joints, urethra, and gallbladder. These symptoms eventually resolve without causing permanent damage.
Doctors diagnose Kawasaki disease when children have at least 4 out of 5 defined symptoms (see How Do Doctors Diagnose Kawasaki Disease?).
Blood tests and cultures of the blood and throat are also done to rule out other disorders that cause similar symptoms (such as measles, scarlet fever, and juvenile idiopathic arthritis).
Doctors who specialize in treating children's heart disorders (pediatric cardiologists) or infectious diseases are often consulted.
Once Kawasaki disease is diagnosed, children have electrocardiography (ECG) and ultrasonography of the heart (echocardiography) to look for coronary artery aneurysms, leaking heart valves, inflammation of the sac that surrounds the heart (pericarditis), or inflammation of the heart muscle (myocarditis). Sometimes abnormalities do not appear right away, so these tests are repeated 2 to 3 weeks, 6 to 8 weeks, and perhaps 6 to 12 months after symptoms began. If ECG or echocardiography tests are abnormal, doctors may do a stress test. If an aneurysm is seen during echocardiography, children may have heart catheterization.
With treatment, children recover completely if their coronary arteries are not affected within the first 8 weeks of illness. For children with coronary artery problems, the outcome varies with the severity of the disease. However, with early treatment, almost no children with Kawasaki disease in the United States die.
Without treatment, the death rate is about 1%. Of the children who die, death nearly always occurs in the first 6 months but can occur as long as 10 years later.
About two thirds of the aneurysms go away within 1 year. Large aneurysms are more likely to remain. However, even when aneurysms go away, children have an increased risk of heart problems in adulthood.
Treatment for Kawasaki disease is started as soon as possible. Treatment given within the first 10 days of symptoms significantly reduces the risk of coronary artery damage and speeds the resolution of fever, rash, and discomfort. For 1 to 4 days, high doses of immune globulin are given by vein, and high doses of aspirin are given by mouth. As soon as the child has no fever for 4 to 5 days, the dose of aspirin is lowered but still given for at least 8 weeks from the beginning of illness. If there are no coronary artery aneurysms and signs of inflammation are gone, aspirin may be stopped. However, children with coronary artery abnormalities require long-term treatment with aspirin.
Because aspirin use increases the risk of Reye syndrome in children who have influenza or chickenpox, doctors make sure to give children on long-term aspirin therapy the recommended annual influenza vaccination. All children should also receive the varicella (chickenpox) vaccine at the appropriate ages. If children are exposed to or contract influenza or chickenpox, dipyridamole is sometimes temporarily used instead of aspirin to lessen the risk of Reye syndrome.
Children with large coronary aneurysms may be treated with drugs that prevent the blood from clotting (anticoagulants).