Fulminant myocarditis and sudden death associated with thymoma-related autoimmunity.

Fulminant myocarditis (FM) is a severe, rapidly progressive and life-threatening condition of myocarditis associated with infectious or autoimmune etiologies. Here, we present three patients with an invasive thymoma who had FM, which eventually led to sudden death. The most frequent clinical presentations at onset include palpitations, orthopnea, and acute worsening of myasthenia gravis (MG). Highly elevated myocardial biomarkers and positive autoantibodies against cardiac muscle, skeletal muscle, and neuromuscular junctions were detected in serum. The electrocardiograph (ECG) findings progressed to life-threatening ventricular arrhythmias. Although high-dose methylprednisolone or intravenous immunoglobulin was administered along with advanced respiratory support, profound hemodynamic collapse rapidly occurred, and these patients eventually died within days. This case series underscores the importance of rapid recognition of FM associated with thymoma and early aggressive supportive and immunomodulatory interventions, including consideration of mechanical circulatory support when clinically indicated.