480. Alternate Diagnoses in Children Evaluated for Multisystem Inflammatory Syndrome in Children (MIS-C)

Background SARS-CoV-2 infection is typically a mild illness in children. Multisystem inflammatory syndrome in children (MIS-C) is a rare, post-infectious, hyperinflammatory condition associated with SARS-CoV-2 infection. The presentation of MIS-C is nonspecific and diagnostic criteria is broad. The Centers for Disease Control (CDC) defines MIS-C as a hospitalized patient < 21 years presenting with fever, laboratory evidence of inflammation, no alternative plausible diagnosis, and with positive exposure history or testing for current or recent SARS-CoV-2 infection. Since there is no single diagnostic test for MIS-C, there are other disease processes that can mimic its presentation and delay prompt diagnosis and management.Methods Between March 2020 and February 2021, we reviewed 282 charts of patients admitted for evaluation of MIS-C at our institution.Results 101 were found to have MIS-C, 45 found to have Kawasaki Disease (KD), and 129 were ruled out. Of the ruled-out group, the most common final diagnoses were viral infection, urinary tract infection, and acute SARS-CoV-2 infection. Other diagnoses included rickettsial infections, pneumonia, rheumatologic conditions, and bloodstream infection. Rhinovirus/enterovirus, adenovirus, Epstein-Barr virus (EBV), and Herpes Simplex Virus (HSV) were the most common viruses other than SARS-CoV-2 identified. Conclusion These findings highlight the importance of maintaining a broad differential when evaluating a patient for MIS-C, especially as community seroprevalence rises, making antibody presence less predictive of MIS-C.Disclosures Susan Wu, MD , Eli Lilly (Shareholder)