RESUMEN
Coronavirus disease 2019 (COVID-19) mRNA vaccine-related cases of pericarditis and myocarditis have been reported infrequently. Most of the patients usually present within a week of the vaccine, and on average, most of the cases were reported after the second dose of vaccine within two to four days. Chest pain was the most common presentation, and fever and shortness of breath were the other commonly reported symptoms. The patients can have positive cardiac markers and electrocardiogram (EKG) changes, and the cases can be mistaken for cardiac emergencies. We present a 17-year-old male patient with sudden onset substernal chest pain for two days who got the third dose of the Pfizer-BioNTech mRNA vaccine within 24 hours prior. EKG was remarkable for diffuse ST elevations, and troponins were elevated. Later, the cardiac magnetic resonance imaging confirmed the findings of myopericarditis. The patient was treated with colchicine and non-steroidal anti-inflammatory drugs (NSAIDs), completely recovered, and is doing fine to date. This case hights that post-vaccine myocarditis can be mistaken and early diagnosis and management can prevent unnecessary interventions.