Clinical Overview of Multisystem Inflammatory Syndrome in Children

Signs and symptoms

• Patients with MIS-C usually present with fever and some combination of abdominal pain, vomiting, diarrhea, skin rash, and mucocutaneous lesions (i.e., conjunctivitis). In severe cases, children can present with hypotension and shock.^1-3 
• Patients with MIS-C have elevated laboratory markers of inflammation (e.g., C-reactive protein, ferritin); many have laboratory markers indicating damage to the heart (e.g., elevated troponin), and many have low platelet or absolute lymphocyte counts (thrombocytopenia and lymphopenia, respectively).^1-3
• Some patients develop cardiac dysfunction (e.g., decreased left ventricular function) and coronary artery dilatation or aneurysm.^1,2,4 
• Gastrointestinal inflammation can manifest as abdominal pain, vomiting, and diarrhea; children may have signs and symptoms similar to those of acute appendicitis.⁵
• Neck pain has also been described, sometimes with development of phlegmon on radiographic imaging.⁶
• Children with MIS-C can also have neurologic involvement which is usually transient and presents as headache or altered mental status.^7,8
• Other severe neurologic manifestations may include encephalopathy, stroke, demyelination, and fulminant cerebral edema, although this is rare.^7,8
• Not all children will have the same signs and symptoms, and some children may have symptoms not listed here. MIS-C may begin weeks after a child is infected with SARS-CoV-2. The child may have been infected from an asymptomatic contact, and, in some cases, the child and their caregivers may not even know they had been infected.

Reducing risk

MIS-C and vaccination

• Multiple studies^9-11 have found that COVID-19 vaccination is effective at reducing the risk of MIS-C, with one CDC study finding that two doses of Pfizer-BioNTech COVID-19 vaccine had a greater than 90% estimated effectiveness at preventing MIS-C.¹² See How to Protect Yourself and Others for information on staying up to date with COVID-19 vaccinations.

• CDC has also created Considerations for Initiating COVID-19 vaccination in people with a history of MIS-C.

• While MIS-C following vaccination is very rare,¹³ CDC and FDA require that MIS-C occurring after COVID-19 vaccination be reported to the Vaccine Adverse Event Reporting System.

Resources

• Clinical Outreach and Communication Activity (COCA) Webinar, Dec 8, 2022: Updates on Multisystem Inflammatory Syndrome in Children (MIS-C): Epidemiology, Case Definition, and COVID-19 Vaccination
• MMWR Recommendations and Reports: CSTE/CDC Surveillance Case Definition for MIS-C in Children Associated with SARS-CoV-2 Infection — United States