Acute myocarditis usually presents with a broad spectrum of symptoms and has variable clinical outcomes. A proportion of acute myocarditides may develop into fulminant myocarditis resulting in significant mortality if left untreated. This case report describes an unusual presentation of fatal lymphocytic myocarditis mimicking a thoracic aortic dissection in a previously healthy 45-year-old male. Fulminant myocarditis should be considered as part of the differential diagnosis in an acutely unwell young adult presenting to the Emergency Department with non-specific symptoms.