The Centers for Disease Control and Prevention (CDC) defines MIS-C as
An individual under 21 years presenting with fever, laboratory evidence of inflammation and evidence of clinically severe illness requiring hospitalization, with multisystem (two or more) organ involvement (cardiac, renal, respiratory, hematologic, gastrointestinal, dermatologic or neurological); AND
No alternative plausible diagnoses; AND
Positive for current or recent SARS-CoV-2 (COVID-19) infection by reverse-transcriptase polymerase chain reaction (RT-PCR), serology or antigen test; or COVID-19 exposure within the four weeks prior to the onset of symptoms.
MIS-C symptoms include persistent fever, inflammation and evidence of organ dysfunction or shock.
Some children present with features similar to Kawasaki disease or toxic shock syndrome. Other common features include cytokine storm, abnormal clotting, poor heart function, diarrhea, gastrointestinal symptoms, acute kidney injury and shortness of breath suggestive of congestive heart failure.
Lab results may show inflammatory markers in the blood, lymphopenia under 1,000, thrombocytopenia under 150,000, neutrophilia, elevated B-type natriuretic peptide (BNP) or N-terminal prohormone BNP, hyponatremia or elevated D-dimers.
The AAP recommends measurement of vital signs, assessment of perfusion and oxygen saturation as part of a patient’s initial evaluation. Clinicians should consult and coordinate with infectious disease or rheumatology early in the process. Clinicians also may consider laboratory screening for systemic inflammation and initial lab screenings such as a complete blood cell count with differential, urine analysis, erythrocyte sedimentation rate, C-reactive protein, ferritin, lactic acid dehydrogenase, comprehensive metabolic panel, pro-BNP, troponin and fibrinogen.
Because MIS-C is rare, children with symptoms also should be evaluated for other infectious and noninfectious conditions. COVID-19 testing should be performed with RT-PCR assay and serologic testing.
Children who are sick enough to warrant hospital admission may need an expanded laboratory and cardiac workup. Some may develop hemodynamic compromise and need intensive care.
Infection control and reporting
Clinicians should follow local infection-control policies when caring for a patient under investigation for COVID-19 including those with suspected MIS-C. If the condition is diagnosed, it should be reported to the local public health department.
Treatment and follow-up
The AAP recommends using a multidisciplinary approach to guide treatment. Patients have been treated with intravenous immunoglobulin, steroid therapy and biologics. Concurrent antibiotic therapy also is common. Treatment/prophylaxis for clotting also may be needed. Starting two to three weeks after discharge, patients with MIS-C should have close outpatient pediatric cardiology follow-up.