1st March 2024

A 3-year-old girl has presented to the emergency department with sudden knee swelling after a fall

A 3-year-old girl has presented to the emergency department with sudden knee swelling after a fall. The knee is tender and boggy. Aspiration of the knee reveals a large haematoma. Urgent coagulation tests reveal a normal PT with prolonged aPTT, while clotting factor studies reveal significantly reduced factor VIII levels. Her father shares a similar condition, but her mother has been tested and does not carry the same mutation responsible for the condition.

Given the likely diagnosis, which of the following likely contributed towards her condition?

Select the SINGLE most appropriate option from the list below. Select ONE option only.