New findings in COVID-related kids' syndrome, Kawasaki disease - CIDRAP

In the largest known cohort of MIS-C patients and their distributions across the United States, the cumulative incidence was 2.1 per 100,000 people 21 and younger and varied by state, from 0.2 to 6.3 per 100,000.

Patients 18 to 20 years had the most severe MIS-C signs and symptoms, with 30.9% having myocarditis, 36.4% having pneumonia, and 18.2% having acute respiratory distress syndrome (ARDS).

In contrast, children 0 to 4 years old had the fewest severe MIS-C signs and symptoms, but 38.4% had low blood pressure or shock, and 44.3% required intensive care.

Gastrointestinal symptoms, rash, and conjunctival hyperemia (an inflammatory eye condition) occurred in 53% to 67% of MIS-C patients.

"The geographic and temporal association of MIS-C with the COVID-19 pandemic suggested that MIS-C resulted from delayed immunologic responses to SARS-CoV-2 infection," they wrote.

The researchers called for development of lab markers or diagnostic tests to distinguish MIS-C from severe COVID-19 and other inflammatory conditions such as Kawasaki disease.