Objectives: Diagnostic between multisystem inflammatory syndrome associated with COVID-19 in children (MIS-C) and Kawasaki disease (KD) can make difficulties due to many similarities. Our study aimed to create a Kawasaki/MIS-C differentiation score (KMDscore) allowing discrimination of MIS-C and KD.Study design: The retrospective multicenter cohort study included clinical, laboratory, and instrumental information about MIS-C (n = 72) and KD (n = 147). The variables allowed to discriminate both conditions used to construct and validate the diagnostic score called the KMDscore.Results: Patients with MIS-C were older, had earlier admission to the hospital, had a shorter time before fever resolution, two times frequently had signs of GI and CNS involvement observed, and had more impressive thrombocytopenia, higher level of CRP, ferritin, ALT, AST, LDH, creatinine, triglycerides, troponin, and D-dimer compared to KD patients. Respiratory signs in MIS-C were presented with pleuritis, acute respiratory distress syndrome, oxygen dependency, lung infiltration, and ground-glass opacities in CT. The heart involvement with fast progression of myocarditis provided the severity of MIS-C and ICU admission due to 12 times higher arterial hypotension or shock and required cardiotonic. No differences in the frequency of CA lesions were seen in the majority of cases. Five criteria, CRP >11 mg/dl (18 points), D-dimer >607 ng/ml (27 points), age >5 years (30 points), thrombocytopenia (25 points), and GI involvement (28 points), were included in the KMDscore. The summa >55 points allowed to discriminate MIS-C from KD with a sensitivity of 87.5% and specificity of 89.1%.Conclusion: The KMDscore can be used to differentiate the diagnostic of MIS-C from KD.

ObjectivesHeart involvement in multisystem inflammatory syndrome associated with COVID-19 in children (MIS-C) is a new challenging problem, requiring fast and reliable diagnostics and appropriate treatment. The aim of this study is to describe heart involvement in patients with MIS-C.Study DesignIn this retrospective, multicenter cohort study, data of 122 patients were included. All patients met WHO and CDC criteria of MIS-C.ResultsVarious types of heart involvement in MIS-C patients were observed. Patients with solely coronary artery lesions (CAL, n = 10, 8.2%) had typical features of Kawasaki disease: younger age, thrombocytosis and normal ferritin level, without giant CA aneurysms, thrombosis, myocardial infarction, shock, and ICU admission. Patients with solely myocardial involvement (MI, n = 30, 24.6%) had an older onset age, elevated ferritin, LDH, the highest D-dimer, H score, and thrombocytopenia level. The following clinical signs were associated with MI: gastrointestinal and central nervous system disorder, sore throat, swelling face, splenomegaly, shock, and treatment in the intensive care unit required. Patients with a combination of CAL and MI (n = 10, 8.2%) had symptoms similar to patients with solely MI, except for impressive thrombocytopenia. Shock and ICU admission were found in 34.7% of patients without heart involvement (n = 72, 59%). One major criterion [troponin > 32 pg/ml (52 points)] or at least two minor criteria [face swelling (32 points) and D-Dimer > 1,300 ng/ml (29 points)] were associated with MI (>32 points) with a sensitivity of 67.5% and a specificity of 88.9%.ConclusionThe above-suggested criteria can be added to routine diagnostic procedures to confirm MI in MIS-C patients.

During the COVD-19 pandemic, some pediatric patients in many countries around the world experienced a syndrome resembling a severe Kawasaki disease (KD), often accompanied by shock. Due to the incomplete signs of the classic KD in the era before the present pandemic, in many publications from European countries and the United States, this condition was called «multisystem inflammatory syndrome in children – MIS-C» or «hyperinflammatory shock» or «Kawasaki-like syndrome». This syndrome with a new coronavirus infection is characterized by refractory fever, frequent gastrointestinal symptoms, heart damage (including coronary dilation in some patients, and acute left ventricular failure in the majority), increased ESR and CRP levels, neutrophilia, extremely high troponin levels, increased ferritin, AST, ALT, lactate dehydrogenase, creatine phosphate kinase, interleukin-6 and interleukin-10, coagulopathy with an increase in D-dimer and fibrinogen, thrombocytopenia, sometimes procalcitonin increase. The manifestations of a cytokine storm may meet the criteria for secondary hemophagocytic syndrome. The mechanism of myocardial damage remains unclear. Treatment with high-dose intravenous immunoglobulin is effective, and in the presence of signs of hemophagocytic syndrome, dexamethasone or methylprednisolone. Further research is needed to understand the pathogenesis, resemblance and differences of this syndrome with classic KD, understanding of heart injuiry and early recognition for the need of urgent care.