Compared to adults, children are observed to be less affected by the coronavirus disease, and some experts theorize premature immunity. However, a rare symptom among pediatric patients has been reported. Doctors have found that COVID-19 may be triggering Kawasaki disease in children.
The hallmark symptom of Kawasaki disease linked to COVID-19 was unveiled by the American Heart Association (AHA), a nonprofit organization. A few pediatric patients of COVID-19 were detected with pediatric inflammatory conditions exclusively found among children. As such, clinicians initially thought the children had Kawasaki disease, but the onset of symptoms might be induced by the novel coronavirus itself. The unique link between the two diseases is now being investigated worldwide.
What is Kawasaki Disease?
According to the Centers for Disease Control and Prevention (CDC), a US agency, Kawasaki disease (KD) is an acute febrile disorder that typically affects children younger than five years of age. Although medical researchers know it is a febrile disorder due to fever, they have no concrete evidence of its main cause. Some associate the disease with autoimmunity, while others correlate it to external forces like infections. Regardless of the main cause, KD happens around the globe during the winter and spring seasons. Japan has the highest incidence rate of KD while boys are more commonly afflicted than girls.
The symptoms of KD include a fever, skin rash, swelling of the hands and feet, and inflammation of the oral cavity. Because the symptoms pinpoint inflammation, experienced doctors can diagnose KD based on the physical presentation and if the fever lasts longer than five days. The confirmation of KD is usually from the patient's response to the standard treatment: immunoglobulin and aspirin.
In the US, an estimated 4,248 children under 18 years of age were diagnosed and hospitalized due to KD in 2000, in which 3,277 or 77% were children younger than five years. In 2009, approximately 5,447 children were hospitalized due to KD, and 4,040 of them were children younger than five. Overall, the incidence rate of KD in the country is between 9 and 19 per 100,000 children younger than five years.
COVID-19 and Kawasaki Disease
At AHA, surprising reports of inflammation among pediatric patients were being linked to COVID-19. For some unknown reason, doctors considered that the novel coronavirus might be inducing KD in children. The inflammatory signs contrasted most pediatric COVID-10 patients who commonly develop mild symptoms at worse. But a few pediatric cases in Europe and the US involved severe inflammatory syndrome, which resulted in intensive care.
Preliminary findings in those cases expressed the inflammatory syndrome as KD. The syndrome was a combination of a fever for at least five days, swollen lymph nodes, skin rash, and inflammation. Moreover, children who developed KD-like symptoms might not even test positive of COVID-19. This has been the main confusion among doctors who encountered these hospitalized children.
"We want to reassure parents – this appears to be uncommon. While Kawasaki disease can damage the heart or blood vessels, the heart problems usually go away in five or six weeks, and most children fully recover. Rarely, but sometimes, the coronary artery damage persists. Because of this, Kawasaki disease is the most common cause of acquired heart disease in children in developed countries. Prompt treatment is critical to prevent significant heart problems," explained Dr. Jane Newburger, AHA Young Hearts Council member and Director of the Kawasaki Program at Boston Children's Hospital.
Aside from KD, there were other pediatric cases of severe inflammation reported in hospitals. The inflammation in those cases was closer to toxic shock syndrome, a rare life-threatening condition normally caused by bacterial toxins. The toxins could result in a sudden drop in blood pressure and multiple organ failure if not treated immediately.
"We were laboring under the impression young people were not affected by Covid-19. ... We're not so sure that that is the fact anymore," said Andrew Cuomo, Governor of New York, as quoted by American news channel CNN.
According to the Morbidity and Mortality Weekly Report of the CDC, between February 12 and April 2, 2020, out of 149,760 laboratory-confirmed cases of COVID-19 in the US as of April 2, 2020, 149,082 cases were noted with patient age. Out of that, 2,572 cases were pediatric patients aged younger than 18 years. Among 2,572 pediatric cases, 813 cases were children aged 15 to 17 years, 682 cases were children aged 10 to 14 years, and 1,077 were children aged zero to nine years. Among pediatric cases of patients younger than 10 years of age, 398 cases were children younger than one year, 291 cases were children aged one to four years, and 388 cases were children aged five to nine years.
Immune Response to COVID-19 in Research
Most features of SARS-CoV-2, the virus of COVID-19, are still unknown to scientists. But some studies have been able to provide insights that may be used in clinical settings. At Northwestern University, a private research university in the US, researchers supported the potential role of vitamin D in COVID-19 mortality. Their findings might also explain why some healthy adult patients were likely to develop immune-related complications.
As an immune regulator, vitamin D promoted proper immune response during infection. When an infection has been identified, the hormone helps immune cells do their jobs. After the infection has abated, the hormone orders immune cells to stand down to avoid tissue damage. So, low levels of vitamin D might create an imbalance in immune response, wherein immune cells overexpress an inflammatory chemical called cytokine, which could lead to cytokine storm syndrome.
However, children lack the same immunity level that adults have. Their premature immunity might explain why they are unlikely to develop cytokine storm syndrome. Conversely, adults lacked unknown mechanisms to develop KD. Their mature immunity somehow corrects errors that might be related to pediatric-exclusive inflammation.
If those are true, KD would be an exclusive complication of COVID-19 in children. On the other hand, cytokine storm syndrome would be the exclusive one for adults, especially young, healthy adults. This would push for new treatment guidelines for COVID-19 that doctors could use on patients who might develop immune-related complications in different age groups.