system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
An 18-month-old boy is presented to the emergency department by his parents due to swelling in his right knee after playing in the park. His parents say there was no obvious injury. After questioning, the mother says that an uncle of hers had similar problems. The vital signs include heart rate 146/min, respiratory rate 26/min, temperature 37.1°C (98.8°F) and blood pressure 90/52 mm Hg. On physical examination, the swelling of the right knee is evident. The rest of the physical findings are unremarkable. The ultrasound is compatible with the hemarthrosis of the right knee. The complete blood count (CBC) results are as follows:
Hemoglobin 12.2 g/dL
Hematocrit 36%
Leukocyte count 7,300/mm3
Neutrophils 45%
Bands 3%
Eosinophils 1%
Basophils 0%
Lymphocytes 44%
Monocytes 2%
Platelet count 200,000/mm³
The coagulation test results are as follows:
Partial thromboplastin time (activated) 52.0 s
Prothrombin time 14.0 s
Reticulocyte count 1.2%
Thrombin time < 2 seconds deviation from control
What is the most likely diagnosis?
assistant
Hemophilia A