Many children with serious inflammatory disease did not show COVID-19 symptoms: study

Many children who developed a mysterious inflammatory illness after a COVID-19 infection did not display some of the traditional COVID-19 symptoms, and the disease only appeared several weeks after the infection, according to the largest analysis of U.S. cases to date.

The study of more than 1,700 young children and teenagers led by the Centers for Disease Control and Prevention (CDC) found that most experienced asymptomatic or mild COVID-19 prior to the onset of the disease, called Multiple Inflammatory Syndrome in Children (MIS-C).

The researchers evaluated 1,733 of the 2,090 cases of the syndrome in people age 20 and younger that had been reported to the CDC as of January.

Of the 1,075 patients for whom information about initial COVID-19 illness was available, only 265 had symptoms at that time. 

Most patients with MIS-C presented with fever, signs of generalized inflammation, low blood pressure and multiple organ dysfunction. More than 90 percent of those young people experienced symptoms involving at least four organ systems, and 58 percent needed treatment in intensive care units.

The study, published in JAMA Pediatrics, found that the MIS-C appeared anywhere from two to five weeks after the initial COVID-19 infection. A hyper-inflammatory response coincided with peak antibody production, several weeks after their initial SARS-CoV-2 infection.

Researchers found 95 percent of patients developed MIS-C within 60 days of having a COVID-19 infection. 

While rare, MIS-C is serious. About 38 percent of patients with it in the 0-4 age group developed low blood pressure or shock and about 44 percent were admitted to intensive care.

Overall, respiratory symptoms such as cough, shortness of breath and chest pain were reported in less than 30 percent of patients. 

About 51 percent of patients had low blood pressure, and 37 percent developed shock. Cardiac dysfunction, involving their heart’s inability to pump adequately was reported in 31 percent. 

However, the study found that a significantly higher proportion of patients without preceding COVID-19 symptoms developed hypotension, shock and cardiac dysfunction and were admitted to intensive care, compared with those who had initial coronavirus symptoms.

In a separate op-ed accompanying the study, Jennifer Blumenthal, a pediatric intensivist and pediatric infectious disease specialist at Boston Children’s Hospital, said it shows that pediatricians should not take the lack of prior COVID-19 symptoms as a reassurance that a child is risk-free from MIS-C.

“If the entirety of the world’s pediatric population is at risk for COVID-19 and vaccination will be delayed in the pediatric population compared with adults, this potentially severe outcome must remain at the forefront of the differential diagnosis for pediatricians across the world pending further outcome research,” Blumenthal wrote.

However, she said health care professionals can be reassured by the findings that younger patients had fewer cardiovascular complications and admissions to the intensive care unit.