Kawasaki Disease

What happens in Kawasaki disease

The immune system becomes overactive and inflames the walls of medium-sized arteries. Its cause is unknown. The leading theory is that an infection or environmental trigger sets off an abnormal immune response in genetically susceptible children. It is not contagious, and it is not caused by anything parents did.

In the coronary arteries, inflammation can weaken the wall so it balloons out, forming an aneurysm. Clots can form in aneurysms, or scarring can later narrow the artery, leading to a heart attack years later. Kawasaki disease is the leading cause of acquired heart disease in children in the US and other developed countries.

Kawasaki disease symptoms

Classic criteria

Doctors diagnose classic (complete) Kawasaki disease when a child has fever for at least 5 days plus at least 4 of these 5 features:

The features may come and go and do not all appear at once, so parents' photos and descriptions are useful.

Other common signs

• Marked irritability, often more than the fever explains
• Joint pain or swelling
• Belly pain, vomiting, diarrhea, or a swollen gallbladder
• Redness or crusting at an old BCG vaccine scar, a helpful clue in children vaccinated against tuberculosis

Incomplete Kawasaki disease

Some children, especially infants under 6 months and older children, have fever with only 2 or 3 of the features. This incomplete form carries the same heart risk and is easy to miss. Doctors use blood tests and an echocardiogram to decide whether to treat.

Phases

1. Acute phase (weeks 1 to 2): fever and the main features.
2. Subacute phase (weeks 2 to 4): fever settles, skin peels, platelets rise, and aneurysms are most likely to appear.
3. Convalescent phase (weeks 6 to 8): signs fade and blood tests return to normal.

Diagnosis

There is no single test. Diagnosis combines the clinical features with:

• Blood tests: raised CRP and ESR, raised white cells, anemia, low albumin, raised liver enzymes, and a high platelet count after the first week
• Urine test: white cells without infection
• Echocardiogram: an ultrasound of the heart that measures coronary artery size, compared with normal values for the child's body size (z-score), and checks for heart inflammation and valve leaks
• ECG

Conditions that can look similar include scarlet fever, measles, adenovirus, toxic shock syndrome, drug reactions and MIS-C, a COVID-related inflammatory syndrome.

Kawasaki disease vs MIS-C

Treatment

Treatment happens in hospital and should start as soon as the diagnosis is made, ideally within 10 days of fever onset.

• Intravenous immunoglobulin (IVIG): a single infusion of antibodies from donated blood that calms the inflammation. It lowers the rate of coronary aneurysms from about 25% to around 4 to 5%.
• Aspirin: used under close medical supervision, at higher doses during the fever and then a low dose for several weeks. This is one of the few times aspirin is given to children. Never give aspirin to a child unless a doctor has prescribed it.
• Corticosteroids: added for children at high risk of heart damage, such as infants or those with aneurysms at diagnosis.
• For fever that persists 36 hours after IVIG: a second IVIG dose, steroids, infliximab or other immune treatments.
• Children with aneurysms may need longer-term blood thinners and cardiology care.

While on aspirin, children should get the flu vaccine (inactivated) and avoid exposure to flu and chickenpox, because of a small risk of Reye syndrome. Live vaccines such as MMR and chickenpox are usually delayed for 11 months after IVIG, since the antibodies can stop them working.

Follow-up and outlook

An echocardiogram is repeated at about 1 to 2 weeks and 4 to 6 weeks after treatment. Children with normal coronary arteries at that point usually need no further heart follow-up beyond healthy lifestyle advice. Children with aneurysms are followed by a pediatric cardiologist for life, with the level of monitoring based on aneurysm size.

Most children recover fully without heart damage. Small aneurysms often shrink back to normal size within 1 to 2 years. Giant aneurysms carry long-term risk of clots and heart attack and need lifelong care. Recurrence is uncommon, at a few percent.

Kawasaki disease in adults is rare. Adults who had it as children with coronary changes should tell their doctors, as it can cause coronary artery disease earlier in life.

Frequently asked questions

What are the first symptoms of Kawasaki disease?

It usually starts with a sudden high fever that lasts at least 5 days and responds poorly to fever medicine. Within a few days most children develop red eyes without discharge, a rash, red cracked lips or strawberry tongue, swollen red hands and feet and a swollen neck gland. Marked irritability is very common.

Is Kawasaki disease contagious?

No. It does not spread from child to child, and siblings do not need to be kept apart. Cases sometimes cluster in winter and spring, which suggests an infectious trigger, but the disease itself is an immune reaction rather than an infection that can be passed on.

Can Kawasaki disease be cured?

Yes, in the sense that the acute illness ends and most children recover completely, especially with early IVIG treatment. Any coronary artery damage, however, can persist and needs long-term follow-up. Children without aneurysms after 6 weeks are considered to have the same outlook as other children.

What is incomplete Kawasaki disease?

It means a child has prolonged fever but fewer than 4 of the 5 classic features. It is more common in babies under 6 months, who are also at higher risk of heart damage. Doctors use blood tests and echocardiography to diagnose and treat it in the same way as classic Kawasaki disease.

Can adults get Kawasaki disease?

It is very rare in adults, with only occasional cases reported, and other conditions are usually considered first. More often, adults are affected by the long-term coronary consequences of Kawasaki disease they had as children, which can cause chest pain or heart attack at a young age.