A 67-year-old woman presented with new bilateral leg swelling and was diagnosed with bilateral deep vein thromboses. Rivaroxaban was started at 15 mg twice daily. Ten days later, the patient experienced increased right foot swelling, pain, and cyanosis (Figure). On admission, a right leg arterial ultrasound was normal, but a compression venous duplex ultrasound revealed extensive venous thrombosis of the entire leg. Laboratory evaluation revealed new thrombocytopenia (19,000 cells/mL, reference range 150,000-450,000 cells/mL), reduced renal function (estimated glomerular filtration rate 54 mL/min/m2, reference range >60 mL/min/m2), elevated D-dimer (>20,000 ng/mL, reference range <250 ng/mL), low fibrinogen (106 mg/dL, Clauss; reference range 200-430 mg/dL), elevated soluble fibrin monomer complex (31 μg/mL; reference range <7.9 μg/mL) and elevated prothrombin time (18.8 seconds, reference range 9.5-13.8 seconds), consistent with intravascular coagulation and fibrinolysis. Haptoglobin was low (<14 mg/dL, reference range 30-200 mg/dL), but blood smear did not show microangiopathic hemolytic anemia. Hypercalcemia, vertebral fracture, and chest computed tomography showing probable metastatic disease were consistent with active cancer. Rivaroxaban was discontinued and intravenous unfractionated heparin was initiated with target-activated partial thromboplastin time of 55-90 seconds (reference range 28-38 seconds). Fibrinogen levels rose to >300 mg/dL after transfusion of 2 units of cryoprecipitate, 2 units of fresh, frozen plasma, and one unit of apheresis platelets in the first 8 hours from her initial labs, and she required no further fibrinogen transfusions.