A diagnosis of multisystem inflammatory syndrome in children should be made in the appropriate context and after ruling out other infectious causes. At the same time, clinicians should be diligent as the initial presentation can be unusual and the clinical picture can evolve over time. We report a case that was initially diagnosed as a retropharyngeal infection that did not improve on appropriate antimicrobial coverage. However, as the clinical picture evolved, the patient was found to have multisystem inflammatory syndrome in children and appropriately responded to immunomodulatory treatment. Pediatric infectious diseases practice has been significantly affected by the COVID-19 virus and multisystem inflammatory syndrome in children; data are still emerging as the pandemic evolves. We report this case and conduct literature review to expand the body of evidence about the association between multisystem inflammatory syndrome in children and retropharyngeal involvement.

Background Pediatric patients are more likely than adult patients to experience mild COVID-19 infection but may still suffer severe infection with lasting sequalae or death. One treatment modality is monoclonal antibodies (MABs), which prevent viral replication by binding the epithelial surface receptor for the SARS-CoV-2 spike protein. The Food and Drug Administration (FDA) issued emergency use approval (EUA) for multiple MAB regimens. Clinical trials have shown decreasing viral loads and reductions in hospitalization and death in high-risk adult COVID-19 patients after MAB administration, yet casirivimab/imdevimab (C/I) and bamlanivimab/etesevimab (B/E) have decreased efficacy against Omicron compared to other variants. There is insufficient literature studying MABs in clinical practice among the pediatric population. Methods This study seeks to fill this knowledge gap by reporting the experiences and outcomes with MAB administration of a single pediatric tertiary care center in Rhode Island.Our retrospective case-series documents all mild-to-moderate COVID-19-infected patients who received MABs at Hasbro Childrens Hospital in Providence, RI from January 2021 to March 2022. Included patients had at least one risk factor for severe COVID-19 infection as indicated by the FDA EUA. Results Overall, 108 patients received MABs. Out of the 108 patients, 97 had COVID-19, 11 received post-exposure prophylaxis, 62 patients received B/E, 36 received C/I, 9 received B, and 1 patient received Sotrovimab. Regarding comorbid conditions, 65 had 1 condition and 43 had 2+ conditions. The most common comorbidities were obesity (48), chronic lung disease (37), and immunocompromised state (33). There were 7 cases of infusion-related reaction that resolved during observation in the infusion site. In all, 101 patients completed their recovery at home without events, 1 patient was admitted to the ICU for worsening respiratory status, 3 patients presented to the ED for worsening symptoms and were discharged home, and 3 patients presented for unrelated symptoms within 28 days. Conclusion This study suggests MABs are well-tolerated and effective for preventing severe COVID-19 infection or death among high-risk pediatric patients and for decreasing the health burden of COVID-19 during surges. Disclosures All Authors: No reported disclosures.