To summarize the epidemiology and clinical characteristics of multisystem inflammatory syndrome in children (MIS-C) cases in 26 states.

A total of 186 pediatric patients admitted to 38 sites in 26 states that were participating health centers in the Overcoming COVID-19 study and members of the Pediatric Acute Lung Injury and Sepsis Investigators Pediatric Intensive Care Influenza and Emerging Pathogens Subgroup. The case definition of MIS-C included 6 criteria: serious illness leading to hospitalization, an age of <21 years, fever that lasted for at least 24 hours, laboratory evidence of inflammation, multisystem organ involvement, and evidence of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), antibody testing, or exposure to persons with SARS-CoV-2.

Prospective and retrospective surveillance was used. Statistical analysis was performed to report the frequency of clinical features, laboratory findings, and treatments among patients stratified by SARS-CoV-2 test results, age, and clinical presentation.

A total of 186 patients were included on the basis of case definition. The median age was 8.3 years old, 62% were male, and 73% had previously been healthy. Overall, 70% were positive for SARS-CoV-2 by reverse transcription polymerase chain reaction or antibody testing. The most common system involvement included the gastrointestinal, cardiovascular, hematologic, mucocutaneous, and respiratory. In terms of clinical management, 80% received intensive care, 20% received mechanical ventilation, and 48% received vasoactive support. Treatment included the use of intravenous immune globulin in 77%, glucocorticoids in 49%, and interleukin 6 or 1RA inhibitors in 20%. Kawasaki disease–like features were documented in 40%.

MIS-C affects previously healthy children and adolescents and includes multiple organ system involvement.

The pathogenesis of MIS-C is still being investigated. Cardiac involvement appears common in MIS-C, and coronary artery dilation has been noted. The long-term cardiac sequelae of MIS-C is still unknown.