We report the case of 23-year-old man with mitral valve regurgitation and Glanzmann thrombasthenia, who underwent mechanical mitral valve replacement. Warfarin therapy was devastating, causing bilateral hemothorax, pericardial effusion, gastrointestinal bleeding, and hematuria. Redo mitral valve replacement with a biological prosthesis was required to resolve this critical situation. To our knowledge, this is the first report of mitral valve replacement in Glanzmann thrombasthenia, highlighting the danger of oral anticoagulation in this pathology.