Phase 1 · Understand the Body — Why the disease behaves the way it does.
The One-Line Truth
The whole disease in one chain
Everything on this page exists to explain this line.
A child's immune system misfires 2–6 weeks after COVID, attacking the body instead of finishing cleanup — inflammation floods everywhere at once, mimicking Kawasaki disease but hitting older kids harder.
The Fire Alarm That Won't Turn Off
Imagine a fire alarm system in a building: firefighters (immune cells) arrive to fight a real fire (COVID-19 virus), extinguish it completely, and should leave once the all-clear is given. But in MIS-C, the alarm's 'off' switch is broken — the referees (regulatory T cells) who normally tell firefighters to go home never show up. So the firefighters keep spraying water and foam everywhere, even though there's no fire. The water (cytokines like IL-6 and TNF-alpha) floods the building, soaks into the walls (endothelium, the blood vessel lining), makes pipes burst and leak (capillary leak and vasodilation), damages the building's pump system (the heart and its coronary arteries), and eventually causes the whole structure to collapse (shock and organ failure). The fire is gone, but the response to the fire destroys the building.
CDC MIS-C case definition and clinical guidance · American Academy of Pediatrics (AAP) MIS-C interim guidance · WHO preliminary case definition for multisystem inflammatory syndrome in children · American College of Rheumatology MIS-C clinical guidance · reviewed 2026-07-07