Kawasaki disease

Published by Bupa's Health Information Team, October 2010.

This factsheet is for parents of children who have Kawasaki disease, or for people who would like information about it.

Kawasaki disease usually affects children aged between six months and five years. It causes the blood vessels, including arteries, veins and capillaries, to become inflamed (vasculitis). It can affect any part of the body, and commonly affects the heart. It's the most common cause of acquired heart disease in children in the developed world.

About Kawasaki disease

Kawasaki disease is named after the Japanese doctor, Dr Tomisaku Kawasaki, who first identified it in 1967.

It mainly affects children living in the developed world and is most common among children of North Asian descent. In the UK around eight in 100,000 children have Kawasaki disease and it's more common in boys than in girls.

The exact cause of Kawasaki disease is unknown despite much research.

Most children make a full recovery from Kawasaki disease after several weeks. However, associated heart complications mean that some children are left with long-term health problems or, very rarely, die because of damage to their heart. A very small number of children may get the disease again.

Symptoms of Kawasaki disease

When your child first gets the disease, he or she may suddenly have a fever higher than 102.2°F (39°C) which lasts longer than five days. Your child may also be much more irritable than at other times when he or she previously had a fever. The other main symptoms your child may have are:

• red, bloodshot eyes caused by conjunctivitis, but with no pus
  
• blotchy, red rash mainly on the trunk of your child's body or on the genitals which disappears when pressed
  
• reddened, dry or cracked lips
  
• a red, inflamed tongue with circular white patches that look like a strawberry, often with a red sore throat
  
• large swollen lumps (lymph glands) on either side of your child's neck
  
• swollen hands and feet which become red and hard, often resulting in peeling skin on the fingertips and toes two to three weeks after the disease has started

If your child has any of these symptoms, see your doctor immediately.

You may also notice that your child has other symptoms, including:

• runny nose
  
• cough
  
• sore tummy
  
• vomiting
  
• diarrhoea
  
• painful or swollen joints

Complications of Kawasaki disease

The most important complication of Kawasaki disease is damage to your child's heart and blood vessels. Without treatment about one in four children go on to develop heart disease.

The arteries in your child's heart can become inflamed causing a coronary artery aneurysm. This is when a main blood vessel supplying blood to the heart muscle becomes damaged and swells due to the pressure of blood flowing through it. This creates a balloon-like bulge in the artery which can burst and be fatal. This risk is greatly reduced by early treatment. The length of time your child's fever lasts is often an indicator of whether or not they will develop a coronary artery aneurysm.

Further damage to the heart can develop in the later stages of the disease as your child's body tries to heal itself. Complications can include thrombosis or stenosis. These reduce or stop blood flow to the heart altogether, which can cause reduced ability of the heart to contract properly, or a heart attack.

All these can lead to long-term health problems for your child, and in rare cases, can be fatal. Kawasaki disease can potentially cause problems in adult life too, such as heart disease or heart attacks. However, the risk of long-term complications isn't yet fully known.

Causes of Kawasaki disease

Doctors still don't know what causes Kawasaki disease. However, it's thought that it may be caused by an infection. This is because it frequently occurs in outbreaks during late winter and early spring. It may also be genetic - some children may be genetically more susceptible to the infection than others.

Diagnosis of Kawasaki disease

Kawasaki disease can be difficult to diagnose as many of the symptoms overlap with those of other common childhood diseases, such as measles. There are currently no tests available that can confirm the condition.

Your doctor will ask about your child's symptoms and examine him or her. He or she may also ask you about your child's medical history.

Your doctor will make a diagnosis of Kawasaki disease if your child:

• has a fever lasting longer than five days
  
• doesn't have any signs of other diseases that could be causing the symptoms
  
• has four or more of the main symptoms

As the number of children with Kawasaki disease has increased in recent years, coupled with its dangerous complications, doctors are very careful in making a diagnosis. Therefore your doctor may diagnose incomplete Kawasaki disease if your child has had a fever for more than five days but only has two or three main symptoms. This is because the symptoms may not appear at the same time, or the disease hasn't yet fully developed. This diagnosis is more often made if your child is under the age of one.

If your doctor suspects that your child has Kawasaki disease, he or she will urgently refer your child to a paediatrician, a doctor specialising in children's health.

The paediatrician will review your child and the diagnosis. If confirmed, he or she will arrange for your child to have an echocardiogram. This uses an ultrasound probe, which is run over your child's chest to get a moving picture of the heart. The echocardiogram will show whether your child has developed a coronary artery aneurysm and how well the heart muscle is working.

Treatment of Kawasaki disease

Your child will be given treatment as quickly as possible after diagnosis because of the potentially damaging complications.

Treatment aims to reduce the inflammation in your child's body to relieve symptoms and to prevent a coronary artery aneurysm from forming. This is done using two medicines - immunoglobulin and aspirin.

Immunoglobulin

Immunoglobulin (also known as gamma globulin) is concentrated antibodies from a number of blood donors. It has been shown to be extremely effective in treating Kawasaki disease, and to greatly reduce the likelihood of a coronary artery aneurysm if it's given within 10 days of the symptoms starting.

Immunoglobulin is given as a single dose over a few hours. A smaller dose over five successive days may occasionally be given if heart complications are suspected. The doctor will inject the drug into your child's vein using a cannula (a small plastic tube) and an infusion pump. Occasionally your child may develop side-effects, such as fever or flu-like symptoms.

You will often see some improvement in your child within 24 hours. If your child's fever doesn't go down, his or her doctor may give another dose of immunoglobulin.

Corticosteroids

If your child's fever continues after two courses of immunoglobulin treatment, your child may be given steroids. However, more research is needed to confirm their effectiveness.

Aspirin

Your child will be given four doses of aspirin to take at regular intervals through the day. It's important that you follow your doctor's instructions precisely when giving your child medicines.

Once your child's fever has settled, the dose of aspirin can be reduced. However, he or she will need to continue taking regular doses for a minimum of a further six weeks. The length of time your child will need to continue taking aspirin depends on whether or not his or her coronary arteries have been damaged. If there is damage, your child may need to take aspirin for much longer.

After your child's treatment

Most children make a full recovery within six weeks. At home, your child will need enough fluids to prevent dehydration and lots of rest.

If your child does have lasting heart damage, he or she will need further long-term monitoring and treatment such as:

• echocardiograms - to check his or her heart after diagnosis
  
• anticoagulants - these are medicines that prevent blood clots forming in damaged arteries - your child may have to take them for up to 18 months to allow the arteries to heal

Very rarely, your child may need surgery such as:

• coronary artery bypass graft - where blood is carried away from damaged arteries
  
• angioplasty - where blocked arteries are widened, sometimes using a stent to hold the artery open

For answers to frequently asked questions on this topic, see Common questions.

For sources and links to further information, see Resources.