A mother brings her 6 year-old boy to the emergency room with a swollen left knee joint. He denies a history of trauma to the knee. He reports similar swellings in the right knee joint, right and left elbow joints. Many times he feels the bleeding before he notices the swelling. For the last few days, he has been passing very red colored urine. In the physical examination, you notice a warm, swollen, erythematous left knee joint with severe effusion. There is sensory loss over the lateral and anterior thigh. The quadriceps muscle is weak and small compared to the muscle on his right lower extremity. Patellar reflex is absent. Upon direct questioning, the mother reports that her brother suffers from a bleeding disorder, with frequent nosebleeds. Many of her relatives also have similar bleeding disorders, affecting mostly males. Laboratory tests reveal a normal bleeding time, a normal prothrombin time but a prolonged PTT. As you review the labs with the patient, he developed a severe headache, unrelenting vomiting, and slurred speech. A gross physical examination showed focal neurologic deficits. What is the next best step in the management of this patient?
