A Mysterious Fever and Retropharyngeal Edema on a Previously Healthy 10-Year-Old Boy Without Known Exposure to COVID-19.

Multisystem inflammatory syndrome in children (MIS-C) is considered a late manifestation of COVID-19 infection, and it is a diagnosis of exclusion after ruling out other causes of systemic inflammations. We present a case of MIS-C to highlight the importance of cardiac workup in MIS-C due to frequent cardiac involvement and discuss the possible association between retropharyngeal edema and MIS-C. The case patient is a 10-year-old previously healthy boy who presented with persistent fever, right-side neck pain, and a new rash. The rash was attributed to recent amoxicillin use by his parents. Pertinent workups included elevated inflammatory markers, a benign electrocardiogram test, a negative urine analysis, blood culture, and retropharyngeal edema by computerized tomography. On day four of hospitalization, the patient failed to improve with broad-spectrum antibiotics and became tachycardic. A repeat echocardiogram revealed a decreased ejection fraction with mitral valve regurgitation. The cardiac finding, the skin finding, the persistent fever, and the initial negative workups fulfilled the case criteria for MIS-C. A positive test for anti-SARS-CoV-2 spike protein receptor-binding domain antibodies confirmed the diagnosis, and the patient improved with intravenous immune globulin (IVIG) and steroids. The retropharyngeal edema was thought to be coincidental; however, there seem to be frequent associations between MIS-C and retropharyngeal edema, suggesting that the retropharyngeal edema could be one of the initial manifestations of MIS-C. More study is needed to study the association between retropharyngeal edema and MIS-C and shed light on the diagnosis and medical management of MIS-C.