What is Kawasaki disease?
Kawasaki disease is a rare condition that mainly affects children under the age of five. It is also known as mucocutaneous lymph node syndrome.
The condition causes virus-like symptoms that don't respond well to medication.
The characteristic symptoms of Kawasaki disease are a high temperature that lasts for more than five days with:
- a rash
- swollen glands in the neck
- dry, cracked lips
- red fingers or toes
- red eyes
See your doctor if your child is unwell with the above symptoms. The symptoms of Kawasaki disease can be similar to those of other conditions that cause a fever in children.
Kawasaki disease cannot be prevented but if it is diagnosed and treated promptly, most children will make a full recovery within six-to-eight weeks.
Read more about diagnosing Kawasaki disease.
It is thought that Kawasaki disease is caused by an infection, although the exact cause is not fully understood. Read more about the causes of Kawasaki disease.
Treating Kawasaki disease
Kawasaki disease is usually treated in hospital because it can sometimes lead to serious complications.
It is best if treatment begins as soon as possible, ideally within 10 days of the symptoms starting. The sooner treatment starts, the quicker the recovery time and the less risk there is of complications developing.
Aspirin and intravenous immunoglobulin (a solution of antibodies) are the two main medicines that are used to treat Kawasaki disease.
Read more about treatment of Kawasaki disease.
Complications of Kawasaki disease
Kawasaki disease causes the blood vessels to become inflamed and swollen, which can lead to complications in the coronary arteries (the blood vessels that supply blood to the heart).
Up to 5% of children who have Kawasaki disease experience complications with their heart. In about 1% of cases, the complications can be fatal.
Read more about the complications of Kawasaki disease.
Symptoms of Kawasaki disease
The symptoms of Kawasaki disease usually develop in three phases over a six-week period.
The three phases are described below.
Phase 1: acute (weeks 1-2)
Your child's symptoms will appear suddenly and may be severe.
The first and most common symptom of Kawasaki disease is usually a high temperature (fever) of 38C (100.4F) or more.
The fever can come on quickly and doesn't respond to antibiotics or antipyretics (medicines that are used to reduce a fever, such as ibuprofen or paracetamol). If your child has a fever, they may be very irritable.
Your child's fever will usually last for at least five days. However, without treatment, it can last for around 11 days. In some rare cases, the fever can last for as long as three-to-four weeks.
The fever may come and go and could possibly reach a high of 40C (104F).
Your child may have a blotchy, red rash on their skin. It usually starts in the genital area before spreading to the trunk (torso), arms, legs and face.
The spots are usually red and raised but there will not be any blistering (fluid-filled pockets of skin).
Hands and feet
The skin on your child’s fingers or toes may become red or hard and their hands and feet may swell up.
Your child may feel that their hands and feet are tender and painful to touch or to put weight on, so they may be reluctant to walk or crawl while these symptoms persist.
Conjunctival injection is where the whites of the eyes become red and swollen. Both eyes are usually affected but the condition isn't painful.
Unlike conjunctivitis, where the conjunctiva (the thin layer of cells that cover the white part of the eye) becomes inflamed, fluid does not leak from the eyes in conjunctival injection.
Lips, mouth, throat and tongue
Your child’s lips may be red, dry or cracked. They may also swell up and peel or bleed.
The inside of your child’s mouth and throat may also be inflamed. Their tongue may be red, swollen and covered in small lumps (strawberry tongue).
Swollen lymph glands
If you gently feel your child's neck, you may be able to feel swollen lumps on one or both sides. The lumps could be swollen lymph glands.
Lymph glands are part of the immune system, which is the body’s defence against infection. They may swell to over 1.5cm wide, feel firm and be slightly painful.
Phase 2: sub-acute (weeks 2-4)
During the sub-acute phase, your child's symptoms will become less severe but may last longer.
The fever should subside but your child may still be irritable and in considerable pain. Symptoms during the the second phase of Kawasaki disease may include:
- peeling skin on the fingers and toes (also sometimes on the palms or soles of the feet)
- abdominal pain
- urine that contains pus
- feeling drowsy and lethargic (lacking energy)
- joint pain and swollen joints
- jaundice (yellowing of the skin and whites of the eyes)
It is during the second phase of Kawasaki disease that complications are more likely to develop, such as a coronary artery aneurysm (a bulge in one of the blood vessels that supply blood to the heart).
Read more about the complications of Kawasaki disease.
Phase 3: convalescent (weeks 4-6)
Your child will begin to recover during the third phase of Kawasaki disease, which is known as the convalescent phase.
Your child's symptoms should begin to improve and all signs of the illness should eventually disappear. However, your child may still be listless (lack energy) and may become easily tired during this time.
Occasionally, complications can develop during the third phase of Kawasaki disease but they are more likely to develop before this stage.
Causes of Kawasaki disease
The cause of Kawasaki disease is not fully understood, but the condition is thought to be caused by an infection.
The symptoms of Kawasaki disease are similar to those of an infection. This means that bacteria or a virus may be responsible. However, so far, a bacterial or viral cause hasn't been identified.
As Kawasaki disease isn't contagious, it can't be passed from one person to another. Therefore, it is unlikely to be caused by a virus alone.
Kawasaki disease doesn't usually affect babies under six months old, although sometimes very young children can develop the condition. This suggests that newborn babies are protected by antibodies passed on to them by their mother, either before birth or during breastfeeding. Antibodies are proteins that destroy disease-carrying organisms.
As there are very few older children and adults who are affected by Kawasaki disease, they may be immune to whatever causes it. Although many people are exposed to Kawasaki disease, only a few go on to develop the symptoms.
The children who develop Kawasaki disease may be genetically predisposed to it. This means that the genes they inherit from their parents may make them more likely to get the condition.
One theory is that rather than there being a single gene responsible for Kawasaki disease, it may be the result of many genes that each slightly increase the chances of a child developing the condition.
There is currently research being carried out that is trying to identify the genes that may be responsible.
One theory is that Kawasaki disease may be an autoimmune condition (where the immune system attacks healthy tissues and organs).
Other theories suggest that Kawasaki disease may be a reaction to certain medications, or environmental pollutants such as chemicals or toxins (poisons).
Diagnosing Kawasaki disease
There is no single test to diagnose Kawasaki disease. Your doctor will confirm the condition by looking at your child's symptoms and carrying out a physical examination.
The National Institute for Health and Clinical Excellence (NICE) states that your child may have Kawasaki disease if they have a high temperature (fever) of 38C (100.4F) or above for longer than five days, and they have at least four of these key symptoms:
- conjunctival injection in both eyes: where the whites of your child’s eyes are red and swollen
- changes to the mouth or throat: such as dry, cracked lips or a red, swollen tongue
- changes to the hands and feet: such as swollen or painful hands or feet, or red or peeling skin on the palms of the hands or soles of the feet
- a rash
- swollen lymph nodes in the neck
The skin on your child’s fingers or toes may become red or hard and their hands and feet may swell up. Your child's hands and feet may also be tender and painful to touch or to put weight on, so they may be reluctant to walk or crawl.
Read more about the symptoms of Kawasaki disease.
In some cases, Kawasaki disease may also be diagnosed even if a child does not have four or more of the key symptoms listed above. It may be that they have atypical (irregular) or incomplete Kawasaki disease.
If your child only had a fever for four days but they have four or more of the key symptoms, a diagnosis of Kawasaki disease may also still be made.
Your child may need to have further tests to rule out other conditions that could be causing their symptoms. Possible conditions that your child could have include:
- scarlet fever: a bacterial infection that causes a distinctive pink-red rash
- toxic shock syndrome: a rare, life-threatening bacterial infection
- measles: a highly infectious viral illness that causes a fever and distinctive red-brown spots
- glandular fever: a viral infection that can cause a fever and swollen lymph glands
- Stevens-Johnson syndrome - a very severe allergic reaction to medication
- viral meningitis: an infection of the protective membranes (meninges) that surround the brain and spinal cord
There are also several tests that can be carried out during the first 7-10 days to help support a diagnosis of Kawasaki disease.
Individually, these tests may not be conclusive but when combined with some of the key symptoms listed above, they can help to confirm a diagnosis.
White blood cell count
A sample of your child’s blood will be tested to see how many infection-fighting white blood cells it contains.
In over 50% of cases of Kawasaki disease, the blood contains a higher number of white blood cells than normal.
The number of platelets (clotting cells) in the blood may also be tested as part of the diagnosis.
The platelet count is usually at its highest during the second or third week of Kawasaki disease. A platelet count may not help diagnose Kawasaki disease during the first two weeks but it can be used to confirm a diagnosis later on.
A urine sample may be tested to see whether it contains white blood cells, which could indicate Kawasaki disease. If your child has Kawasaki disease, their urine is unlikely to contain any bacteria in it.
C-reactive protein (CRP) is produced by the liver at the start of an infection or inflammation in the body. The amount of CRP in the blood can be measured. An increased level indicates inflammation or an infection.
A CRP test cannot identify the condition that is causing the inflammation but it can confirm whether there is a problem.
Erythrocyte sedimentation rate
The erythrocyte sedimentation rate (ESR) is a measure of how much inflammation there is in the body.
To calculate your child’s ESR, a blood sample will be placed in a test tube. The length of time it takes for the red blood cells to sink to the bottom of the tube will be recorded.
If the red blood cells sink faster than normal, it may mean that your child has an inflammatory condition, such as Kawasaki disease.
Like a CRP test, ESR can only indicate whether there is inflammation in the body but it cannot identify what is causing it.
Cerebrospinal fluid (CSF) is the protective fluid that surrounds the brain and spinal cord.
A procedure called a lumbar puncture is where a sample of CSF is taken by inserting a needle between the vertebrae (back bones) of the lower spine.
The fluid will then be tested for white blood cells which, if present, could also be a sign of Kawasaki disease.
Other blood tests
A sample of your child’s blood may also be tested to determine levels of:
- sodium (salt)
- enzymes (proteins that speed up and control chemical reactions)
- lipid (fats)
If the blood sample contains abnormal amounts of any of these, it could be a sign of Kawasaki disease.
Complications of Kawasaki disease usually affect the heart. Therefore, your child may need to have some tests to check that their heart is functioning normally. These might include an:
- electrocardiogram (ECG), which measures the heart's electrical activity using electrodes (flat metal discs) that are attached to the arms, legs and chest; an ECG can identify damage to the heart or problems with the heart's rhythm
- echocardiogram, which involves ultrasound (high-frequency sound waves) used to produce images of the heart which can confirm whether there are any problems with the heart’s structure or function
During the acute phase of Kawasaki disease (weeks 1-2), several heart abnormalities may be identified. These could include:
- tachycardia (a rapid heart rate)
- pericardial effusion (a collection of fluid in the heart)
- myocarditis (inflammation of the heart muscle)
In around 25% of cases of Kawasaki disease, the blood vessels around the heart (the coronary arteries) are widened slightly.
In most cases, these abnormalities will resolve six-to-eight weeks after the condition starts, although in some people further complications can develop.
Kawasaki disease treatment
Kawasaki disease is usually treated in hospital because it can cause serious complications. Treatment should begin as soon as possible.
If Kawasaki disease is not treated promptly, it may take longer for your child to recover. Their risk of developing complications will also be increased.
Aspirin and intravenous immunoglobulin are the two main treatment methods used to treat Kawasaki disease.
Your child may be prescribed aspirin if they have Kawasaki disease. This is one of the few occasions where aspirin may be recommended for a child under 16 years old.
Unless it is prescribed by a healthcare professional treating your child, never give your child aspirin.
Aspirin is a non-steroidal anti-inflammatory drug (NSAID). It is used to treat Kawasaki disease because:
- It can ease pain and discomfort.
- It can help reduce a high temperature (fever).
- At high doses, aspirin is an anti-inflammatory (it reduces swelling).
- At low doses, aspirin is an anti-platelet (it prevents blood clots from forming).
The dose of aspirin that your child is prescribed and how long they need to take it for will depend on their symptoms. They will probably be given high-dose aspirin until their fever subsides.
They may then be prescribed a low dose until six-to-eight weeks after the start of their symptoms. This is to prevent coronary artery abnormalities (problems developing in the blood vessels that supply blood to the heart).
Research that was carried out into using aspirin to treat Kawasaki disease did not find any evidence either for or against its use. However, it is used because it helps prevent heart complications developing by working both as an anti-inflammatory and an anti-platelet.
Intravenous immunoglobulin is also called IVIG. Immunoglobulin is a solution of antibodies that is obtained from healthy donors. Intravenous means it is injected directly into a vein.
Antibodies are proteins that the immune system produces to fight disease-carrying organisms.
Research has shown that IVIG can reduce fever and the risk of heart problems. The immunoglobulin that is used to treat Kawasaki disease is called gamma globulin.
After your child is given IVIG, their symptoms should improve within 36 hours. If their fever does not improve after 36 hours, they may be given a second dose of IVIG.
Corticosteroids are a type of medication that contain hormones (powerful chemicals that have a wide range of effects on the body). They may be recommended if a second dose of IVIG is ineffective.
Research is currently underway to look at the benefits of using corticosteroids to treat Kawasaki disease. One review of research into corticosteroids found that they can reduce the need to be treated again with IVIG but do not reduce the risk of heart problems.
Read more about corticosteroids.
When your child is discharged from hospital you should be given advice about how to care for them at home. This may include making sure they are as comfortable as possible and ensuring they drink plenty of fluids.
Make sure your child continues taking any medication that has been prescribed for them and look out for any side effects.
Your child will be given a follow-up appointment and their heart will continue to be monitored. Once an echocardiogram (an ultrasound scan of the heart) has confirmed that your child does not have any heart abnormalities, they can usually stop taking aspirin.
Some symptoms, such as peeling skin, may not occur until three-to-four weeks after Kawasaki disease starts and a full recovery could take around six weeks.
Complications of Kawasaki disease
With prompt treatment, most children with Kawasaki disease make a full recovery. However, sometimes complications can develop.
The complications associated with Kawasaki disease are mainly related to the heart. They occur as a result of the inflammatory effect that the condition has on the blood vessels.
Inflammation in the coronary arteries (the blood vessels that supply blood to the heart) can cause a section of the artery wall to weaken.
As the blood passes through the weakened part of the artery wall, the blood pressure causes it to bulge outwards like a balloon. This is called an aneurysm.
Some aneurysms heal by themselves over time. However, sometimes a blood clot (thrombosis) can form in a weakened section of the artery.
This can cause a heart attack (where part of the heart muscle dies because it is starved of oxygen) or heart disease (where the heart's blood supply is blocked or interrupted).
In rare cases, the aneurysm can rupture (burst), which could cause severe internal bleeding.
It is also possible for other major arteries to be affected, such as the brachial artery (the main blood vessel in the upper arm) or the femoral artery (the main blood vessel in the upper thigh).
Around 25% of children with Kawasaki disease who don't receive treatment (for example, due to their condition being incorrectly diagnosed) go on to experience heart-related complications.
For children who receive intravenous immunoglobulin (IVIG) to treat Kawasaki disease, their risk of developing complications is reduced to 5%.
The heart-related complications that are associated with Kawasaki disease are serious and in 1% of cases they may be fatal.
If your child develops a serious heart abnormality, they may require medication or, in some cases, surgery. Possible treatments include:
- anti-coagulant medicines and anti-platelet medicines: medicines that stop the blood from clotting, which may prevent your child having a heart attack if their arteries are particularly inflamed
- coronary artery bypass graft: surgery to divert blood around narrow or clogged arteries and improve the blood flow and oxygen supply to the heart
- coronary angioplasty: surgery to widen blocked or narrowed coronary arteries to improve the blood flow to the heart; in some cases, a stent (a short, hollow metal tube) is inserted into the blocked artery to keep it open
Children with severe complications may have permanent damage to their heart muscles or valves (the flaps that control the flow of blood). They will have regular follow-up appointments with a heart specialist (cardiologist) so that their condition can be closely monitored.
Complications in later life
If your child has had heart complications as a result of Kawasaki disease, they may have an increased risk of developing cardiovascular complications later in life. This includes conditions such as heart attacks and heart disease.
The cardiologist will be able to advise you about your child's likelihood of developing further heart-related problems.