Fulminant Myocarditis and Acute Appendicitis after COVID-19 Vaccination.

A 19-year-old Japanese man was hospitalized for cardiogenic shock 28 days after receiving a second dose of the coronavirus disease 2019 (COVID-19) mRNA-1273 vaccine. He had had a high fever for three days with vomiting and abdominal pain before arriving at our hospital. The patient visited a local hospital and was diagnosed with heart failure and acute appendicitis. An endomyocardial biopsy specimen showed myocarditis. Thereafter, Impella CP left ventricular assist device implantation and venoarterial peripheral extracorporeal membranous oxygenation were initiated immediately along with inotropic support and steroid pulse therapy. Given these findings, he was finally diagnosed with multiple inflammatory syndrome and fulminant myocarditis.