Kawasaki disease is a rare illness that typically strikes children younger than age 5. It is also known as mucocutaneous lymph node disease. Kawasaki disease is a mysterious illness of unknown cause, although some scientists suspect that the cause may be an infection (such as a virus or a toxin from a bacterium. Kawasaki disease was first identified among Japanese children in 1967, and within nine years, the illness had been reported in American children living in Hawaii. Although researchers assume that the Kawasaki disease could have been caused by an infection that was carried between Japan and Hawaii, this has never been confirmed. Recent evidence suggests that inherited (genetic) factors may also be important, but the cause of Kawasaki disease remains a mystery.
Kawasaki disease makes children ill by triggering inflammation in many different parts of the body. In the heart, this inflammation can take the form of myocarditis (inflammation of heart muscle), pericarditis (inflammation of membranes covering the heart) or valvulitis (inflammation of the heart valves). Kawasaki disease can cause a type of meningitis (inflammation of membranes covering the brain and spinal cord), and it can cause inflammation in the skin, eyes, lungs, lymph nodes, joints and mouth. However, the most dangerous problem related to Kawasaki disease is the threat of vasculitis (blood vessel inflammation), especially in the body's medium-sized arteries. This vasculitis can be especially dangerous when it damages the heart's coronary arteries, causing an abnormal widening (dilation) or bulge (aneurysm) in these vessels. In rare cases, artery damage related to Kawasaki disease can significantly interfere with the heart's blood supply, even to the point of causing a heart attack in a very young child.
In the United States and other industrialized nations, Kawasaki disease is now the most common cause of heart disease that is not present at birth in children. . The disease is rather rare, affecting fewer than 1 in 5000 children under the age of 5 in the U.S. Seventy-five percent to 80% of the cases are children under the age of 5 years old. Boys are affected more often than girls.
Because there is no test available to confirm that a person has Kawasaki disease, doctors define the condition by the combination of problems that it produces. The typical person with this disease has a high fever (usually 104 degrees Fahrenheit or above) for at least five days. This fever usually occurs together with at least four of the following additional symptoms:
- Conjunctivitis of both eyes (bloodshot eyes)
- Symptoms involving the mouth or throat, including redness and inflammation of the lips or throat, cracked lips, bleeding lips or a strawberry-colored tongue
- Symptoms affecting the hands or feet, including swelling, redness of the skin on the palms and soles or peeling skin on the fingertips, toes, palms or soles
- A rash, primarily on the torso
- Swollen glands in the neck
People with Kawasaki disease can have other symptoms that are not part of the definition of the disease. These can include:
- Pain and swelling of the joints
- Abdominal pain
- Runny nose
- Weakness in the arms or legs
- Weakness of facial muscles
- Heart rhythm abnormalities
- Signs of heart failure
Because Kawasaki disease is rare in the U.S., doctors will want to check for other illnesses that are more common and cause similar symptoms.
If your doctor suspects that your child has Kawasaki disease, he or she may begin by asking you about:
- Your child's medications, to rule out a drug reaction
- Any recent exposure to someone with strep throat, to rule out scarlet fever, which is caused by a streptococcal infection
- Any recent exposure to someone with measles, to rule out measles (especially if your child has not been immunized against this illness)
- Any recent tick bite, as Rocky Mountain spotted fever may initially cause similar symptoms
As part of the diagnostic workup for Kawasaki disease, your doctor may need to order blood tests and diagnostic procedures to check for other infectious or noninfectious causes of your child's symptoms. Once it becomes clear that Kawasaki disease is a possibility, your doctor may schedule an echocardiogram, a painless test that uses sound waves to outline the heart's structure. This allows the doctor to check for any dilation or aneurysms in the coronary arteries. In some cases, your doctor may recommend coronary angiography, a procedure in which dye is injected into the arteries that supply the heart to look for evidence of aneurysm or narrowing typical of Kawasaki disease.
Your doctor will diagnose Kawasaki disease if your child has symptoms that fit the definition of the illness and if there is no other explanation for these symptoms. Researchers continue to look for a reliable diagnostic test for this illness, but, so far, none is available.
Kawasaki disease lasts for several weeks, progressing through three different stages:
- Acute phase - This is the most intense part of the illness, when symptoms are most severe. It usually lasts one to two weeks.
- Subacute phase - This stage begins when the child's fever, rash and swollen lymph nodes go away. However, the child still feels irritable, has a poor appetite and slight eye redness and may develop peeling skin on the fingers and toes. This stage usually ends three to four weeks after the fever began.
- Convalescent stage - This stage begins when all clinical symptoms are gone, but the results of a blood test called the erythrocyte sedimentation rate (ESR), an indicator that there is still inflammation in the body, remain abnormal. When the ESR results finally return to normal, usually six to eight weeks after the fever began, the convalescent stage ends.
Because the cause of Kawasaki disease is unknown, there is no way to prevent it.
Kawasaki disease is treated with a single dose of gamma globulin, given intravenously (directly into a vein), together with aspirin taken by mouth. Gamma globulin is a purified collection of proteins and antibodies from donated blood. It is not known why it is effective against this disease. The gamma globulin injections may be repeated over several days if fever continues.
The sooner treatment with gamma globulin is started, the better it works. For example, complications of Kawasaki disease, including coronary artery aneurysms, may be prevented with early treatment. But, if started 10 or more days after symptoms begin, gamma globulin treatment may not prevent these aneurysms. Parents generally are warned against giving aspirin to children because it can trigger Reye's disease, a serious disorder that can damage the brain and liver. However, aspirin is the best treatment for Kawasaki disease, so for children with this condition, the benefits outweigh the risk of Reye's disease, which is rare. The child usually continues to take aspirin for six to eight weeks after the acute symptoms of Kawasaki disease subside.
Other treatments, including corticosteroids or immunosuppressive medications, such as etanercept or infliximab, are sometimes recommended if gamma globulin injections are not effective. A procedure called plasmapheresis may be recommended for Kawasaki disease that does not respond to other treatments. In plasmapheresis, blood is removed, filtered to remove proteins (including antibodies) and then returned to the body.
Call your doctor immediately if your child develops a high fever, with or without other symptoms of Kawasaki disease.
Without proper treatment, 20% to 25% of children with Kawasaki disease develop abnormalities in their coronary arteries. With treatment, this percentage drops to 2% to 4%. In general, the risk of death from cardiac complications is about 1% to 2%, most commonly during the first two to 12 weeks of illness.
Up to 25% of people with Kawasaki disease have coronary aneurysms during the first one to three months of illness. The aneurysms often go away on their own within the next year or two. However, coronary artery disease may develop later in previously inflamed coronary arteries. For this reasons, periodic re-evaluation is recommended for all children who have had Kawasaki disease. Children who continue to have symptoms of heart disease (such as chest pain) or coronary abnormalities during the acute illness generally require regular testing, including stress tests, echocardiography and sometimes coronary angiography. If cardiac health deteriorates because of damage to the coronary arteries, surgery may be needed to correct the problem.
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