LAUSR

A 16-year-old previously healthy boy presented to the hospital with chest pain 3 days after his second dose of the BNT162b2 mRNA SARS-CoV-2 vaccine (Pfizer-BioNTech). On admission, he was afebrile with normal vital signs; an Abbott ID NOW COVID-19 test was negative; electrocardiography showed diffuse ST-segment elevation (Picture 1A); echocardiography showed normal left ventricular wall motion and thickness with a small pericardial effusion; and his troponin T level was 3 ng/L. Cardiovascular magnetic resonance (CMR) imaging demonstrated hyperintense pericardium on T2-weighted sequence with fat suppression (Picture 1B, red arrowheads), gadolinium-delayed hyperenhancement of the entire pericardium (Picture 1C, red arrowheads), and midwall hyperenhancement of the interventricular septum (Picture 1C, yellow arrows), indicating pericarditis with slight myocardial involvement. A right ventricular endomyocardial biopsy revealed enhanced extravasation of erythrocytes (Picture 2A-B) without inflammatory cell infiltration in the myocardium (Picture 2C-E). Platelet aggregation was also found in the myocardial microvasculature (Picture 2F).