Tranexamic acid (TXA) is a synthetic lysine derivative that acts as an antifibrinolytic by blocking the binding site of lysine to plasminogen and preventing the conversion to plasmin, which normally lyses polymerized fibrin in blood clots.1 TXA is FDA approved for heavy menstrual bleeding and short-term prevention in patients with hemophilia, but is currently regularly used intravenously to reduce blood loss in a variety of surgical settings, including trauma, orthopedics, transplants, neurosurgery, and obstetrics. This evidence concerns the gene PLG and hemophilia.