Kawasaki Disease

What is Kawasaki disease and who gets it?

Kawasaki disease is an uncommon condition that mainly affects children aged under 5 years. It most commonly affects children aged 9-12 months. It causes various symptoms throughout the body (listed below). Kawasaki disease was first described by a Japanese doctor in the 1960s. Since then cases have been reported in many countries.

What are the symptoms of Kawasaki disease?

A fever (high temperature) which lasts more than 5 days is usual. In addition, at least four of the following normally develop.

• Redness of the eyes (conjunctivitis).
• Changes in the mouth such as a red throat or tongue, or dry and cracked lips.
• A blotchy red rash. This normally fades within a week.
• Changes in the hands or feet such as mild swelling or redness. The skin often peels on some of the fingers or toes after about 2-3 weeks.
• One or more lymph glands in the neck become swollen.

The diagnosis of Kawasaki disease is based on the above typical group of symptoms. There is no test to confirm the disease. Tests may be done to rule out other diseases that cause similar symptoms, such as measles, scarlet fever, etc. Other symptoms may develop in addition to the above. These include diarrhoea, vomiting, abdominal pains, being off food, joint swelling and pains, and jaundice (skin goes yellow). Also, affected children are commonly very irritable.

What causes Kawasaki disease?

The cause is not known. The symptoms seem typical of a virus infection. However, it is not contagious. It is rare for contacts of affected children also to become affected at the same time. This means that the cause is unlikely to be just a virus infection. It may be an unusual or severe reaction to a common virus that usually causes little or no harm to most people. But, no virus or other germ has been proved to cause this disease.

There seems to be some genetic tendency that increases the risk of developing the condition. For example, parents of children with Kawasaki disease are more likely to have had the condition themselves during childhood. Also, brothers and sisters of children with Kawasaki disease have an increased risk of developing the condition. So, a theory is that affected children may have a genetic make-up that makes them 'overreact' to a common virus infection that does not cause problems in most children.

How does the illness progress?

Typically, fever develops first and then the other symptoms (listed above) develop after a few days. Often, the symptoms that develop after the fever has started develop one after each other rather than all coming on at the same time. This is why the diagnosis of Kawasaki disease may take several days to make after the initial fever starts. In total, symptoms tend to last up to 10 days before easing and going, although complications sometimes develop (see below).

During the illness, some children become very unwell, but others have a mild illness similar to many virus infections. However, any child suspected of Kawasaki disease is normally admitted to hospital, even if they appear to have a mild illness. A heart scan is normally done to look for complications (see below). If complications do occur, they usually develop a week or so after the symptoms listed above.

What are the possible complications of Kawasaki disease?

Heart problems

Without treatment, about 1 in 5 children who have Kawasaki disease develops inflammation of the blood vessels to the heart (coronary arteries). This can cause a swelling of a section of an artery which is called an aneurysm.

A coronary artery aneurysm usually causes no symptoms. Over time it often goes away and the artery returns to normal. However, the wall of an aneurysm is weakened and abnormal. Serious problems may develop in some children with an aneurysm. The most serious is that a thrombosis (clot) may develop in the aneurysm and damage the heart (a heart attack). About 1 in 100 children with Kawasaki disease die of heart problems.

An aneurysm can be detected by a heart scan (an echocardiogram). If an aneurysm does occur, it starts to develop a week or more after the fever and other acute symptoms begin. Treatment within 10 days of symptoms starting often prevents this complication. This is why it is important to diagnose and treat Kawasaki disease in the early stages of the illness.

Other complications

The aneurysm of a coronary artery is caused by inflammation of the artery (a 'vasculitis'). This can occur in other arteries in various parts of the body - but is very rare. Various other rare problems have also been reported in some children with Kawasaki disease.

What is the treatment for Kawasaki disease?

• Aspirin. This is one of the few times aspirin is given to children. Aspirin helps to reduce the inflammation in the coronary arteries.
• Gammaglobulin. This is an antibody mixture obtained from human blood. It is given by an infusion into the bloodstream. It is not clear how it works. It may modify the response of the immune system in some way to prevent inflammation in the arteries.

A combination of aspirin and gammaglobulin given within 10 days of the onset of Kawasaki disease reduces the chance of heart complications. Without treatment, about 20 in 100 affected children develop an aneurysm. With treatment, this is reduced to about 5 in 100.

Other treatments aim to make the child comfortable, such as giving lots to drink, and nursing them through the acute feverish illness.

Research continues to search for better treatments. For example, recent research suggests that steroid drugs, abciximab, infliximab and methotrexate may be of benefit to prevent complications. Further research is needed to confirm the role of these drugs in the treatment of Kawasaki disease.

What is the outlook (prognosis)?

Without treatment, most children make a full recovery but complications develop in some cases. With early treatment, complications are much less likely to develop.

Repeat heart scans are usually advised over several weeks. If the heart scan is normal at 6-8 weeks after symptoms began, then long-term heart problems are thought to be unlikely.

Long-term follow-up (such as an annual check-up) may be advised if an aneurysm was detected, as the long-term effect on the heart is not yet fully known.

Further information and support

Kawasaki Support Group

13 Norwood Grove, Potters Green, Coventry, West Midlands CV2 2FR
Tel: 024 7661 2178 Web: www.kssg.org.uk