Table 3.

Comparison between KDSS and MIS-C according to the MMWR CDC report⁴¹

	KDSS*	MIS-C†
Clinical	•KDSS older than KD controls, but younger than MIS-C •62.4% male (similar to KD controls 61.8% males) •1% to 7% of KD cases •Gastrointestinal symptoms (occasional in most series) •Lower prevalence in Asian vs Western countries§ •Higher in Hispanic origin (1 study) •Incomplete KD criteria (1 of 3) in KDSS vs (1 of 4) in KD (ns) •Admitting diagnoses often other than KD •Poor perfusion/shock by definition •Myocardial dysfunction present •PICU stay ∼6 days •Higher resistance to IVIG (44.4%) than KD controls (9.6%) •Coronary abnormalities (39.8%) than KD controls (8.6%) •Longer hospitalization (11 days) than KD controls (5 days) •Longer duration of fever compared with KD controls •1.3% mortality	•Older age median ∼8 years •55.4% male •35.6% of SARS-CoV-2 (CDC); 5.8% of COVID-19 (China)‡ •Gastrointestinal symptoms common (91%) •Predominantly in Western countries •∼40% Hispanic, ∼33% black, ∼13% white •KD-like symptoms, rare complete criteria 4.9% (3% to 6.6%) •A mix of admitting diagnoses (GI, shock, respiratory) •Poor perfusion/shock 35.4% (0% to 75.9%) •Myocardial dysfunction 40.6%, myocarditis 22.8% •PICU stay ∼5 days (IQR: 3-7) •Unknown prevalence of IVIG resistance •Coronary dilatation and aneurysms (18.6%) •Length of hospitalization ∼6 days IQR (4-9) •Duration of fever ∼5 days IQR (3-6) •1.8% mortality
Biological	•Elevated CRP (higher in KDSS compared to KD controls) •Elevated interleukins, TNF-α •Elevated troponin (rarely tested) •Lower platelet count in KDSS compared with KD controls •Elevated WBC count, (unreported lymphocyte count) •Elevated D-dimers (reported) •Elevated BNP/NT-proBNP (when tested) •Macrophage-activation syndrome (reported)	•Elevated CRP •Elevated interleukins, TNF-α •Elevated troponin •Thrombocytopenia •Elevated WBC count with lymphopenia •Elevated D-dimer •Elevated BNP/NT-proBNP •Macrophage activation syndrome (frequently reported)

BNP/NT-proBNP, B-type natriuretic peptide-N-terminal pro-BNP; CDC, US Centers for Disease Prevention and Control; CRP, C-reactive protein; GI, gastrointestinal; IQR, interquartile range; IVIG, intravenous immunoglobulin; KD, Kawasaki disease; KDSS, KD shock syndrome; MIS-C, multisystem inflammatory syndrome in children; MMWR, Morbidity Mortality Weekly Report; PICU, pediatric intensive care unit; SARS-CoV-2, severe acute respiratory syndrome-coronavirus-2 TNF, tumour necrosis factor; WBC, white blood cell.

^⁎Age, male to female ratio, and complete vs incomplete diagnostic criteria for KD are based on the current meta-analysis.

^†As reported by the CDC.⁴¹

^‡“Of 2143 Chinese children diagnosed with laboratory-verified or clinically diagnosed COVID-19, 5.2% had severe disease, and 0.6% had critical disease.”⁵⁰

^§“From 2.6 to 6.95% in Western countries (vs) 1.45% and 1.9% in Taiwan.”⁵