Takeshi Koga^1,, Moe Yoshimura¹, Sakiko Kubo¹, Miki Nagai¹, Katsuhiko Tabata¹, Hiromi Teranishi¹, Misato Fujino¹, Hiroshi Kawana¹, Ikuma Musha¹, Yuko Akioka¹

Our case report presents a young patient vaccinated for coronavirus disease 2019 (COVID-19) who developed multisystem inflammatory syndrome in children (MIS-C), which was later confirmed to be multisystem inflammatory syndrome after vaccination (MIS-V). 15-year-old boy previously infected by COVID-19 who received the first dose of COVID-19 vaccine 50 days later and developed fever, lethargy, headache, diarrhea, nausea, lip swelling, neck pain, and dysphagia. Contrast-enhanced computed tomography revealed a low absorption area with no contrast effect was observed in the posterior pharyngeal gap suggesting retropharyngeal phlegmon. He was diagnosed to be MIS-V level 2 based on the Brighton Collaboration Case Definition and improved by Intravenous immunoglobulin (IVIG). The frequency of neck symptoms in MIS-V is higher than in other febrile diseases, and many cases of retropharyngeal phlegmon are observed. In addition, pediatric COVID-19 is mostly asymptomatic or mild; therefore, it is predicted that children who are unaware of their history of COVID-19 before vaccination are not rare. Therefore, after vaccination, extra care should be required to development of MIS-V in children.

COVID-19, vaccine, MIS-C, neck pain, dysphagia, adverse event following immunization, child