(1) Background: vitamin B1 level depletion, known as a beriberi syndrome, can lead to severe cardiovascular complications, from which perimyocarditis fulminans is one of the most severe. (2) Methods: this is a retrospective case study that includes an adult patient with clinical presentations of acute heart failure (HF) symptoms following perimyocarditis on the grounds of thiamine deficiency. (3) Results: A 49-year-old woman presented with acute HF symptoms due to perimyocarditis. The patient suddenly developed refractory cardiogenic shock with metabolic acidosis requiring maximal medical management, including an intra-aortic balloon pump and extracorporeal membrane oxygenation. Due to additional peripheral polyneuropathy, beriberi disease was suspected after excluding other possible causes of the patient's condition. After administration of vitamin B1, clinical improvement in the patient's condition and the resolution of metabolic abnormalities were observed, which ultimately confirmed the diagnosis of Shoshin syndrome caused by the implementation of a gluten-free diet without indications for its adherence. (4) Conclusions: Fulminant beriberi disease, although considered rare, is a life-threatening condition and should always be included in the differential diagnosis of critically ill patients, notably those with malnutrition. An unbalanced diet can be detrimental and have severe consequences, i.e., perimyocarditis fulminans. However, treatment with thiamine can significantly improve the patient's cardiac function and restore hemodynamic and metabolic parameters.