Table II.

Comparing MIS-C related to COVID-19 (MIS-C) and MSMD

Parameter	CDC MIS-C5	MSMD
Age	<21 y	Early in childhood and rarely in adulthood
Fever	≥38.0°C for ≥24 h, or report of subjective fever lasting ≥24 h	Likely and can occur with weight loss
Hospitalization	Required	Likely
Laboratory	Evidence of inflammation: Lymphopenia, neutrophilia, elevated inflammatory markers (CRP, ESR, IL-6, procalcitonin, ferritin, LDH) Abnormal coagulation (elevated fibrinogen and D-dimer) Hypoalbuminemia	Lymphophilia Elevated inflammatory markers: CRP, ESR, TNF-α, IL-6 Normal coagulation May have hypoalbuminemia
SARS-CoV-2 presence	At least 1 required: Positive by RT-PCR for RNA Positive serological assay for antibodies Positive COVID-19 antigen by antigen assay Exposure to a known case within 4 wk before onset of symptoms	Unlikely except for current COVID-19 pandemic
Blood and tissue cultures	Negative—must exclude other diagnoses	Positive blood and/or tissue cultures Nontypical mycobacteria, Salmonella, Listeria, histoplasmosis, etc
Chest radiography	Not required for diagnosis but may include opacities (ground glass), peribronchial thickening, and/or pleural effusions	Disseminated pulmonary lesions are common
Multisystem involvement	At least 2 organ systems involved (cardiac, renal, respiratory, hematologic, gastrointestinal, dermatologic, or neurological)	Not required but often lymphadenopathy present and multisystem involvement likely with disseminated infections
Genetics	Not found at present	Confirmed by immunodeficiency screen for mutations in IKBKG, IFNGR1, IFNGR2, STAT1, IL12B, IL12RB1, IL12RB2, IL23R, ISG15, IRF8, TYK2, CYBB, RORC, JAK1, and SPPL2A

CDC, Centers for Disease Control and Prevention; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; LDH, lactate dehydrogenase.

MIS-C can be diagnosed if no other diagnosis is possible. Some patients with MIS-C may have overlapping symptoms with complete or incomplete Kawasaki disease.