A 73-year-old woman is evaluated for increasing dyspnea on exertion and left buttock pain of 1 week's duration. She reports pain with standing straight or sitting down. She has no history of trauma. Family history is unremarkable, and she takes no medications.
On physical examination, the patient is pale and displays significant distress by bending over and grasping the back of the chair. Temperature is 36.6 °C (98.1 °F), blood pressure is 140/80 mm Hg, pulse rate is 108/min, and respiration rate is 19/min. A 10-cm hematoma is noted on the left buttock with tracking down the back of the thigh, with smaller ecchymoses scattered over her arms and shins. She has no bleeding of the gums or nose. A stool sample is guaiac negative.
Hematocrit | 35% |
Leukocyte count | 9100/µL (9.1 × 109/L) |
Mean corpuscular volume | 89 fL |
Platelet count | 310,000/µL (310 × 109/L) |
Activated partial thromboplastin time (aPTT) | 90 seconds |
Prothrombin time | 10.3 seconds |
aPTT following 1:1 mixing study with normal plasma | 45 seconds |
Factor VIII activity | 3% (normal, 50%-150%) |
Factor VIII inhibitor | Markedly elevated |
Which of the following is the most appropriate management?