5 Facts About Kawasaki Disease

While most pediatric COVID-19 cases are mild, the disease has been tied to a serious new syndrome in kids. In recent weeks, dozens of children who tested positive for COVID-19 antibodies have exhibited symptoms like rash, fever, diarrhea, and swollen hands and feet—all signs similar to a rare condition called Kawasaki disease. Like Kawasaki disease, the mystery illness, officially known as pediatric multi-system inflammatory syndrome (PIMS), can lead to severe heart issues. In New York, three children have died from it.

Medical experts still aren’t sure how this condition develops, or how it’s related to COVID-19. Here are five things we do know about Kawasaki disease, the syndrome it resembles.

1. Symptoms of Kawasaki disease appear in phases.

When patients first contract Kawasaki disease, the most serious symptom is a high fever that lasts five days or more. Other diagnostic signs that appear in this first stage include chapped lips, bloodshot eyes, sore throat, swollen hands and feet, and a rash covering the back, limbs, belly, and groin. These symptoms are the result of inflammation in the arteries, veins, capillaries, and lymph nodes.

After experiencing a fever for about two weeks, patients may enter the second stage of the disease. This phase is characterized by diarrhea, vomiting, joint pain, and temporary hearing loss. Peeling skin on the hands and feet is another symptom, with dead skin sometimes coming off the extremities in layers.

The third phase is known as the convalescent phase, and it comes about four weeks after the fever first develops. During this period, which can last a couple of weeks, patients gradually recover and their symptoms improve.

2. Kawasaki disease can have deadly complications.

Most children who get Kawasaki disease fully recover, and recovery rates are even higher when the disease is caught early. But in some cases, the illness has dangerous effects on the cardiovascular system. The inflammation that characterizes the disease can weaken artery walls, resulting in rare cases of heart disease and heart attacks in children. Heart problems afflict about a quarter of Kawasaki disease patients who didn’t receive early treatment for the condition. Of these untreated cases, roughly 2 to 3 percent are fatal.

3. Kawasaki disease is uncommon.

Kawasaki disease is rare, effecting roughly 4200 children in the U.S. annually. The syndrome is almost exclusive to kids, with most cases occurring in patients younger than 5 years old. It’s 1.5 times more common in boys, so sex may factor into who gets it. Ethnicity is another possible component: Kawasaki disease rates are 10 to 20 times higher in East Asian countries like Korea and Japan than in the U.S.

4. Kawasaki disease is often treated with an over-the-counter drug.

One of the primary treatments for Kawasaki disease is aspirin. The anti-inflammatory drug can help relieve pain, reduce fever, and prevent blood clots in kids with the condition. Aspirin shouldn’t be taken by children for other types of fever or pain, though, due to the risk of a serious condition called Reye's syndrome. Kawasaki disease is the rare instance when aspirin is given to kids, and even in these cases, it should only be taken under the supervision of a doctor.

The other main treatment for the disease is intravenous immunoglobulin, or IVIG. Immunoglobulin is a solution of antibodies from healthy donors that helps boost the patient's immune system to fight disease. It’s administered through the patient’s vein, and if given early enough, it can reduce symptoms within 36 hours.

5. COVID-19 may trigger Kawasaki disease, but it's too soon to tell.

Doctors are unclear on what causes Kawasaki disease. One theory is that antigens found in some viruses can trigger a hyper-inflammatory response in children who are genetically susceptible. This is similar to what's being observed in the new pediatric multi-system inflammatory syndrome, which is possibly related to COVID-19. "We think patients were exposed to the SARS-CoV-2 virus, they may or may not have had some symptoms, and later on there was a delayed reaction," Michael Portman, pediatric cardiologist and director of the Kawasaki Disease Clinic at Seattle Children’s, says of the recent PIMS cases. "There was a hyper-inflammatory response launched by the body against the viral antigen, so that fits with the main hypothesis for Kawasaki disease."

More research still needs to be done to understand the relationship between PIMS and COVID-19. "It's a little bit early to make a direct link, but it seems plausible that the new coronavirus does trigger an immune response that could result in Kawasaki disease, or a different spectrum of the disease, or even a separate disease that we're calling PIMS," Portman tells Mental Floss.

It's also too early to say definitively that PIMS and Kawasaki disease are the same thing, but to experts who have studied the latter, the new syndrome looks very familiar. "It is very difficult to separate the two," Portman says. "They are very, very similar, and it's going to take quite a bit of research to determine if they're different."