Kawasaki disease is a rare condition that mainly affects children under the age of five. It's also known as mucocutaneous lymph node syndrome.
The characteristic symptoms 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
After a few weeks the symptoms become less severe, but may last longer. At this stage, the affected child may have peeling skin on their fingers and toes.
The symptoms of Kawasaki disease usually develop in three phases over a six-week period.Phase 1: acute (weeks 1-2)
Your child's symptoms will appear suddenly and may be severe.High temperature
The first and most common symptom of Kawasaki disease is usually a high temperature (fever) of 38C (100.4F) or above.
The fever can come on quickly and doesn't respond to antibiotics or medicines typically 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, it can last for around 11 days without the proper treatment. In some rare cases, the fever can last for as long as three to four weeks.
The fever may come and go, and your child's body temperature could possibly reach a high of 40C (104F).Rash
Your child may have a blotchy, red rash on their skin. It usually starts in the genital area before spreading to the torso, arms, legs and face.
The spots are usually red and raised, but there will not be any blistering.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 their hands and feet are tender and painful to touch or put weight on, so they may be reluctant to walk or crawl while these symptoms persist.Conjunctival injection
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 thin layer of cells that cover the white part of the eye (conjunctiva) becomes inflamed, fluid doesn't 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, also known as "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, 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 second phase of Kawasaki disease may include:
- peeling skin on the fingers and toes – also sometimes on the palms of the hands or the soles of the feet
- abdominal pain
- urine that contains pus
- feeling drowsy and lacking energy (lethargic)
- joint pain and swollen joints
- yellowing of the skin and the whites of the eyes (jaundice)
It's during the second phase of Kawasaki disease that complications are more likely to develop, such as a coronary artery aneurysm, which is a bulge in one of the blood vessels that supply blood to the heart.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 have a lack of energy and become easily tired during this time.
Occasionally, complications can develop during the third phase of Kawasaki disease, but they're more likely to develop before this stage.
The cause of Kawasaki disease isn't fully understood, but the condition is thought to be caused by an infection. Genetics may also increase the chance of developing the condition.Infection
The symptoms of Kawasaki disease are similar to those of an infection, so 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. This makes it unlikely that it's 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 few older children and adults are affected by Kawasaki disease, they may be immune to whatever causes it. While many people are exposed to Kawasaki disease, only a few go on to develop the symptoms.Genetics
The children who develop Kawasaki disease may be genetically predisposed to it. This means 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.
Kawasaki disease is more common in children from northeast Asia, especially Japan and Korea. This also suggests there may be a genetic cause.Other theories
One theory is that Kawasaki disease may be an autoimmune condition, where the immune system attacks healthy tissues and organs.
Other theories suggest Kawasaki disease may be a reaction to certain medications or environmental pollutants, such as chemicals or toxins (poisons).
There's no single test to diagnose Kawasaki disease. Your GP will confirm the condition by looking at your child's symptoms and carrying out a physical examination.
The National Institute for Health and Care 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 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 the 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 put weight on, so they may be reluctant to walk or crawl.
In some cases, Kawasaki disease may be diagnosed even if a child doesn't have four or more of the key symptoms listed above. It may be that they have atypical or incomplete Kawasaki disease.
A diagnosis of Kawasaki disease still may be made if your child only had a fever for four days, but they have four or more of the key symptoms.Tests
Your child may need to have tests to rule out other conditions that could be causing their symptoms. Possible conditions 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 that surround the brain and spinal cord (meninges)
- lupus – an autoimmune condition that can cause a range of symptoms, including fatigue, joint pain and a rash
Several tests can also be carried out during the first 7 to 10 days to help support a diagnosis of Kawasaki disease, including:
- a urine sample – to see whether it contains white blood cells
- blood tests – such as a white blood cell count or platelet count
- a lumbar puncture – a sample of cerebrospinal fluid is taken by inserting a needle between the vertebrae of the lower spine
Individually, these tests may not be conclusive, but when combined with some of the key symptoms listed above, they can help confirm a diagnosis.Heart problems
Complications of Kawasaki disease usually affect the heart. This means your child may need some tests to check their heart is functioning normally.
These might include an:
- electrocardiogram (ECG) – which measures the heart's electrical activity using flat metal discs (electrodes) attached to the arms, legs and chest; an ECG can identify damage to the heart or problems with the heart's rhythm
- echocardiogram – this involves 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:
- a rapid heart rate (tachycardia)
- a collection of fluid in the heart (pericardial effusion)
- inflammation of the heart muscle (myocarditis)
In around 25% of cases of Kawasaki disease, the blood vessels around the heart (coronary arteries) are widened slightly.
In most cases, these abnormalities resolve six to eight weeks after the condition starts, although further complications can develop in some people.
Kawasaki disease is usually treated in hospital as it can cause serious complications. Treatment should begin as soon as possible.
It may take longer for your child to recover if Kawasaki disease isn't treated promptly. Their risk of developing complications will also be increased.
The two main treatments for Kawasaki disease are:
- intravenous immunoglobulin
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.
Never give your child aspirin unless it's prescribed by a healthcare professional as it can cause side effects, including Reye's syndrome.
You'll usually be warned not to give your child aspirin to treat a high temperature caused by another illness, such as chickenpox. Aspirin treatment for Kawasaki disease can be restarted when the fever settles.
Aspirin is a non-steroidal anti-inflammatory drug (NSAID). It's 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 antiplatelet – it prevents blood clots forming
The dose of aspirin your child is prescribed and how long they need to take it for depends on their symptoms. They'll probably be given high-dose aspirin until their fever subsides.
They may then be prescribed low-dose aspirin until six to eight weeks after the start of their symptoms. This is to reduce blood clots if there are problems developing in the blood vessels that supply blood to the heart.
Research carried out into using aspirin to treat Kawasaki disease didn't find any evidence either for or against its use. However, it's used because it helps prevent heart complications developing by working both as an anti-inflammatory and an antiplatelet.Intravenous immunoglobulin
Intravenous immunoglobulin is also called IVIG. Immunoglobulin is a solution of antibodies taken from healthy donors. Intravenous means it's injected directly into a vein.
Antibodies are proteins the immune system produces to fight disease-carrying organisms.
Research has shown IVIG can reduce fever and the risk of heart problems. The immunoglobulin 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 doesn't improve after 36 hours, they may be given a second dose of IVIG.Corticosteroids
Corticosteroids are a type of medication that contains hormones, which are powerful chemicals that have a wide range of effects on the body.
They may be recommended if a second dose of IVIG isn't effective. If your child is found to have a high risk of heart problems, they may be treated with corticosteroids as part of the first treatment.
Research is currently looking at the benefits of using corticosteroids to treat Kawasaki disease. The results have been inconsistent, but one review found they can reduce the need to be treated again with IVIG but don't reduce the risk of heart problems.
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.Aneurysm
Inflammation in the blood vessels that supply blood to the heart (coronary arteries) 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 either:
- a heart attack – where part of the heart muscle dies because it is starved of oxygen
- heart disease – where the heart's blood supply is blocked or interrupted
In rare cases, the aneurysm can burst (rupture), which could cause severe internal bleeding.
It's 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.Risk of complications
Around 25% of children with Kawasaki disease who don't receive treatment – because the condition has been diagnosed incorrectly, for example – go on to experience heart-related complications.
The risk of developing complications is reduced for children who receive intravenous immunoglobulin (IVIG) to treat Kawasaki disease.
The heart-related complications associated with Kawasaki disease are serious, and may be fatal in 1% of cases. Children under the age of one are thought to be at higher risk of serious complications.Treating complications
If your child develops a serious heart abnormality, they may require medication or, in some cases, surgery.
Possible treatments include:
- anticoagulant medicines and antiplatelet medicines – medicines that stop the blood 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 – a procedure to widen blocked or narrowed coronary arteries to improve the blood flow to the heart; in some cases, a short, hollow metal tube called a stent 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'll have regular follow-up appointments with a heart specialist (cardiologist) so 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.
If your child has had complications from Kawasaki disease, it's usually recommended that they have follow-up appointments with a specialist.
The cardiologist will be able to advise you about your child's likelihood of developing further heart-related problems.