Mogamulizumab-Associated Acute Myocarditis in a Patient With T-Cell Lymphoma

A 62-year-old woman with human T-lymphotropic virus type 1 cell lymphoma developed heart failure after mogamulizumab, an immunotherapy agent. Clinical presentation and cardiac magnetic resonance imaging were consistent with myocarditis, and a recurrence of heart failure occurred after rechallenge with the therapy. (Level of Difficulty: Advanced.)