285. Differentiating MIS-C from Kawasaki Disease, the second most common vasculitis of childhood

Background: Some clinical and laboratory features of and multisystem inflammatory syndrome in children (MIS-C) have become a major part of the paediatric rheumatology practice. MIS-C is a cytokine storm syndrome that may mimic Kawasaki disease (KD) or may present as a shock-like syndrome. In the presented study we describe the features that may help distinguish KD from MIS-C based on our clinical experience in pediatric patients. Methods: We retrospectively evaluated the MIS-C patients with Kawasaki-like symptoms and those with KD, followed between July 2020 and October 2021 at the Pediatric Rheumatology Department of Hacettepe University Faculty of Medicine, Ankara, Turkey. All MIS-C patients met the criteria for MIS-C defined by the Centers for Disease Control and Prevention (CDC) or the World Health Organization (WHO), and all KD patients met the criteria by the American Heart Association (AHA). Results: The median age of MIS-C patients was older than KD patients. Thirty-one MIS-C patients had positive SARS CoV-2 serology, one had positive PCR and 23 had well-defined exposure to COVID-19. None of the patients with KD had PCR positivity or exposure to COVID-19. Thirty of the MIS-C patients met the criteria for complete KD and the others for incomplete KD. While no difference was found between the median fever duration of the patients, rash (p = 0.044), oral mucosal changes (p = 0.044), and cervical lymphadenopathy (p <0.001) were more frequent in KD. In contrast, MIS-C patients had more acute gastrointestinal symptoms (p <0.001), acute respiratory symptoms (p = 0.044), and low blood pressure (p = 0.002). MIS-C patients had significant lymphopenia (p <0.001) and lower platelet counts than KD patients (p <0.001). MIS-C patients often had high ferritin, D-dimer, troponin, and brain natriuretic peptide (BNP) levels (p