Reactive infectious mucocutaneous eruption is a recently distinguished mucosal-predominant blistering eruption triggered by respiratory infections. We describe a previously healthy 11-year-old Black female with rapidly progressive mucocutaneous blistering after prodromal respiratory infection symptoms. Reactive infectious mucocutaneous eruption was suspected and treated with systemic corticosteroids followed by etanercept. Twenty-four hours after etanercept, the diagnosis of multisystem inflammatory syndrome in children was raised and intravenous immunoglobulin was given. Rapidly worsening mucocutaneous disease ensued but was controlled by a second dose of etanercept. Our case highlights the following: (1) the novel observation of possible interaction/neutralization of etanercept by intravenous immunoglobulin, (2) the challenging differential diagnosis of multisystem inflammatory syndrome in children for reactive infectious mucocutaneous eruption patients in the Coronavirus disease 2019 (COVID-19) pandemic, and (3) the role of early treatment to prevent dyspigmentation.