Kawasaki Disease

Kawasaki disease, also called Kawasaki syndrome, is the leading cause of acquired heart disease in children in the developed world. It usually appears in children under 5 years old. If left untreated, it can result in the formation of a coronary artery aneurysm in up to 30% of cases. With treatment, this complication rate is reduced to about 2%.

Kawasaki disease was first diagnosed in Japan in the 1960s. It can occur in people of any race or ethnic origin, although it is more common in people of Asian descent. It affects mostly children 5 years old and under, although children of any age can get it. Boys are twice as likely to get the disease as girls.

In Canada, about 30 in every 100,000 children under the age of 5 years are diagnosed with Kawasaki disease every year.

Doctors don't know what causes the disease. They believe a virus or some other kind of infection may be responsible for causing the body to mount an "overzealous" immune response, leading to the inflammation of a child's blood vessels (vasculitis) and causing the signs and symptoms of Kawasaki disease.

The disease starts with a fever, usually over 38.5°C (101.3°F). A child with Kawasaki disease also gets irritable and feels sleepy. Sometimes, children have abdominal cramps. After a few days, they also get a rash that can appear anywhere. The rash does not have a specific pattern and may only last a short while. The white part of the eyes get red (conjunctivitis), although there's no discharge. They may also have cracked, dry, reddened lips and a red tongue with enlarged bumps (papillae) that can look a bit like a strawberry. Their hands and feet often swell and become red or purplish-red. Peeling may also occur, especially on the fingers and toes (usually at the top of the nail). Often, some lymph nodes (especially in the neck) become swollen.

Kawasaki disease is dangerous because up to 30% of children with the condition develop complications involving the heart, though this very rarely includes heart attack and sudden death. Complications include abnormal widening (dilation) of the coronary arteries, aneurysm (a bulge in a blood vessel), pericarditis (inflammation of the sac around the heart muscle), and myocarditis (inflammation of the heart muscle itself).

Other complications include inflammation of the tissues around the brain (meninges), the joints, and the gallbladder. The interior of the eye can also get inflamed. All of these other complications usually settle and don't leave any permanent damage.

To be diagnosed with Kawasaki disease, a child must have a fever lasting at least 5 days, along with at least 4 of the following symptoms:

• rash
• red, swollen hands or feet
• changes in the lips (dry, cracked) or mouth (strawberry tongue)
• reddened eyes without discharge (conjunctivitis)
• at least one enlarged, swollen lymph node

Some lab tests may reveal abnormal results that support the diagnosis of Kawasaki disease, although they cannot actually confirm it. There's no set series of lab tests to diagnose Kawasaki disease. Lab tests will be done to check for complications of Kawasaki disease. An ultrasound of the heart (echocardiogram) will always be done around the time of diagnosis. Usually, children who have had Kawasaki disease will get regular follow-up echocardiograms to check for heart damage.

If Kawasaki disease is treated early, there's less of a chance of coronary artery damage. Children with the condition get high doses of intravenous immunoglobulin as soon as the diagnosis is made. They're also given very high doses of acetylsalicylic acid* (ASA). After their fever has gone down, children with Kawasaki disease are given a lower dose of ASA for a few months. This treatment prevents the blood from clotting in case there is some damage to the coronary arteries. Some children may be  given steroids if they have more resistance to immunoglobulin. Live-virus vaccines, such as vaccines for measles, mumps, rubella and chickenpox, should be delayed by about 1 year for children given immunoglobulin since the vaccines may not work as well.

Small coronary artery aneurysms resulting from Kawasaki disease are treated with ASA. For large aneurysms, other blood thinning agents (e.g., warfarin, clopidogrel, or heparin) may be added to the ASA treatment. Small aneurysms go away within a year, but often leave weakened arteries that can cause heart problems in the future. For example, children with Kawasaki disease can have heart attacks 10 years after first being diagnosed with the condition.

If their coronary arteries haven't been damaged, children with the condition can make a complete recovery. Kawasaki disease is fatal in about 1% of cases, where most of the fatalities occur within 6 months of developing heart complications.

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