Comparison of early characteristics of multisystemic inflammatory syndrome and Kawasaki disease in children and the course of Kawasaki disease in the pandemic
Authors: Alkan Fatos , Bircan Onur , Bal Alkan , Bayturan Semra , Zengin Neslihan , Coskun Senol 
Published: July 2024

Abstract
Introduction
Multisystemic inflammatory syndrome (MIS-C) is a newly described disease manifestation in children associated with the novel coronavirus SARS-CoV-2 infection and can be easily confused with Kawasaki disease with its clinical and laboratory findings. In this study, the clinical findings, organ involvements, similarities, and differences in laboratory and imaging of the children with MIS-C and KD at the time of admission will be revealed in detail, and the treatment methods and follow-up results will be revealed.

Material and method
Our study was a single-center study and included pediatric patients who were treated with a diagnosis of MIS-C between March 2020 and July 2023 in the pediatric cardiology, pediatric emergency, pediatric infection, and pediatric intensive care clinics at Celal Bayar University and who were treated with a diagnosis of KD (complete/incomplete) between January 2015 and July 2023. MIS-C diagnosis was made according to the Turkish Ministry of Health COVID-19 guidelines. Sociodemographic characteristics, clinical, laboratory, and echocardiography findings, treatments given, and clinical course of all patients included in the study were evaluated.

Results
The median age was 30 months (7–84) in KD and 96 months (6-204) in MIS-C, and it was significantly higher in the MIS-C group (p = 0.000). Symptom duration was significantly longer in the MIS-C group (p = 0.000). In terms of clinical features, gastrointestinal syndrome findings (nausea, vomiting, abdominal pain) and respiratory findings (dyspnea) were significantly higher in the MIS-C group (p = 0.007, p = 0.000, p = 0.002, respectively). Regarding cardiovascular system involvement, coronary involvement was significantly higher in the KD group. However, valvular involvement, left ventricular systolic dysfunction, and pericardial effusion were significantly higher in the MIS-C group (p = 0.000, p = 0.001, p = 0.003, p = 0.023, respectively). In terms of laboratory findings, white blood cell count was higher in KD (p = 0.000), absolute lymphocyte count, platelet level, blood sodium, and albumin levels were lower in MIS-C group (p = 0.000, p = 0.000, p = 0.000, p = 0.000, p = 0.003, respectively), ferritin and troponin levels were significantly higher in MIS-C group. These results were statistically significant (p = 0.000, p = 0.000, respectively). D-dimer and fibrinogen levels were high in both groups, and no significant statistical difference was detected between the two groups. There was no significant difference between the two groups regarding the length of hospitalization and mortality, but steroid use was significantly higher in the MIS-C group (p = 0.000).

Conclusion
In conclusion, this study has demonstrated the similarities and differences between MIS-C and KD regarding clinical findings, organ involvement, and laboratory and imaging results. The results of our study have important implications in terms of contributing to the data in the existing literature on these two diseases and for the correct diagnosis and better management of pediatric patients presenting with these disorders.

What is known
Multisystemic inflammatory syndrome (MIS-C) is a newly described disease manifestation in children associated with the novel coronavirus SARS-CoV-2 infection and can be easily confused with Kawasaki disease with its clinical and laboratory findings.

What is new
Although MIS-C and KD have many similarities, their symptoms, disease processes, possible complications, and treatment regimens may differ.