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.
Read more about the symptoms of Kawasaki disease.
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.
Your child may need to have further 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.
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.
Read more about the complications of Kawasaki disease.