Q. A 2-month-old boy is brought to the emergency department with recurrent vomiting and lethargy. The symptoms started 4 hours ago. He had vomited the milk repeatedly four times. The mother mentions that he is fed only breast milk and receives no supplements. He was born at home with an uncomplicated delivery. He has reached normal developmental milestones. On examination, he is lethargic and weak, with bulged fontanelle and a swollen left knee. The knee joint is diffusely swollen with ecchymosis but neither tense nor warm. The rest of the physical exam is not significant. The mother mentions that the knee became swollen two days ago following slipping off her lap on the bed. She did not consider it important to mention. His paternal uncle has a coagulation disorder that needs regular treatment, but she does not know what it is. What is the necessary immediate plan for him?