Acute necrotizing eosinophilic myocarditis after COVID-19 vaccination

A 41-year-old male patient who had achieved HIV viral suppression presented with dyspnoea, accompanied by pulmonary oedema on chest X-ray. He developed a high fever and myalgia 10 days after a third-dose BNT162b2 vaccine against COVID-19. The patient had no previous history of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, and the reverse transcription-polymerase chain reaction test for SARS-CoV-2 in nasopharyngeal swabbing specimens was negative. An electrocardiogram showed sinus tachycardia at 110 b.p.m. with diffuse ST elevation, and a laboratory test displayed elevated high-sensibility troponin I level (3087 pg/mL) with marked eosinophilia (3.1 × 103/μL). Echocardiography exhibited diffuse hypokinesis of left ventricular ejection fraction of 50% with left ventricular hypertrophy and pericardial effusion (Panel A). Cardiac magnetic resonance imaging showed abnormal high native T1 (Panel B), hyperintensity on T2-weighted imaging (Panel C), and extensive late gadolinium enhancement (Panel D). These findings were compatible with acute myocarditis. Conventional haematoxylin–eosin section of the endomyocardial biopsy (EMB) specimens revealed widespread infiltration of eosinophils with cardiomyocyte necrosis (Panel E). The oedematous and mildly fibrotic stromal expansion was seen in Masson trichrome section without established scarring (Panel F). A diagnosis was consistent with acute necrotizing eosinophilic myocarditis temporally associated with the COVID-19 vaccine without other specific causes. He was treated with pulse methylprednisolone, followed by oral prednisolone, resulting in clinical improvement and improved left ventricular function. The patient had a good clinical course and was discharged home. The majority of acute myocarditis associated with COVID-19 vaccination reportedly showed lymphocytic myocarditis. The EMB is useful to diagnose hypersensitivity myocarditis. The authors declare that there is no conflict of interest.