The multisystem inflammatory syndrome in children - MIS-C for short - had already emerged during the first coronavirus wave. The syndrome has been known for a long time, not just since the pandemic, Nikolaus Haas told DW  in an interview during the first wave in the spring of 2020. Haas heads the Department of Pediatric Cardiology and Pediatric Intensive Care Medicine at the Ludwig Maximilian University Hospital in Munich.

"In the context of various infectious diseases, patients with a certain predisposition can develop a clinical picture in which the whole body reacts with severe inflammation," he said, which also applies to children. And it's become a more relevant concern during the current pandemic, with one in 5,000 children affected about a month after they suffer from COVID, experts told British daily The Guardian. 

Children of African, Asian descent more affected

The Guardian quotes an unpublished report as saying that of the children worst affected by MIS-C in the UK, about 75% were "black, Asian or ethnic minority (BAME)." According to the data, children do not need to have previously shown any of the classic respiratory symptoms to have MIS-C.

Of 78 patients with MIS-C who were admitted to an intensive care unit, 47% were of Afro-Caribbean origin and 28% were of Asian origin. That's five to six times higher than the respective proportions of these groups of people in the UK population. 

While the number of patients is still relatively small to come to clear statistical conclusions, researchers believe genetics may play a role. Figures by the US Centers for Disease Control (CDC)  also suggest a genetic link.

The CDC data show that 70% of children who were diagnosed with MIS-C were of "Hispanic/Latino" or "black, Non Hispanic" origin. 

The researchers expressed concern that a disproportionate number of people from these groups may have difficulty avoiding exposure to SARS-CoV-2 because of their job or social circumstances. 

The majority of patients had no prior underlying diseases. Medical professionals and researchers are calling for detailed studies to determine why these children are more affected by MIS-C and appear to be at greater risk of developing it.

Early study on MIS-C

In one study, published in The Lancet E ClinicalMedicine  journal on September 1, 2020, a team of doctors from Texas had already evaluated 662 cases from 39 studies in which children had developed the inflammatory disease. The study looked at cases reported worldwide between January 1 and July 25, 2020. 

At that time, the study showed that 71% of the children required treatment in the intensive care unit. 60% suffered severe circulatory shock. Among the nearly 90% who underwent an echocardiogram, doctors found cardiac dysfunction in well over half.

All of the children had a fever, and a large number had abdominal pain or diarrhea and vomiting. 

In this study, in contrast to the Guardian report, the physicians came to the conclusion that the genetic aspect had not yet been conclusively clarified. In principle, the disease could affect everyone.

But experts know from similar illnesses like Kawasaki syndrome that boys and adolescents and those of Asian origin are more susceptible. On the other hand "there was no obvious gender preference in MIS-C, yet individuals with African, African American, or Afro-Caribbean [origin] may have a higher risk," the authors of the Lancet study write.  

Kawasaki syndrome

At first, medical experts assumed that the symptoms the children showed pointed toKawasaki syndrome. This rare disease mainly affects children under the age of five. It has a similar clinical picture to MIS-C and was also known long before the coronavirus pandemic.

There are just over 6,000 cases of it worldwide each year.

The Japanese Tomisaku Kawasaki had  first described the syndrome named after him in 1967. However, the origin of Kawasaki syndrome is still unclear more than 50 years after its discovery.

In this disease, too, there are strong inflammatory reactions in the body with fever above 38.5 degrees Celsius (101.3 degrees Fahrenheit).

Kawasaki syndrome and MIS-C differ mainly in severity.

In Kawasaki syndrome, it's mostly the heart that's affected. Patients have a fever, and liver enzymes go up. The disease can be treated. If therapy is started early enough, vascular damage to the heart can be avoided.

In MIS-C, the kidneys are often affected as well, as are the lungs and liver. Blood tests also show inflammatory reactions, and the white blood cell count increases.

A lot of research is still needed on both diseases ― also to find out whether COVID-19 can be the trigger.

This article was adapted from German.