A 5-year-old boy is brought to the clinic by his parents due…

A 5-year-old boy is brought to the clinic by his parents due to excessive bruising and recurrent joint swelling after minor falls and injuries. His mother reports that he has had prolonged bleeding after minor cuts and a history of painful joint swelling (hemarthrosis). There is no family history of similar symptoms. Laboratory testing reveals: Prolonged activated partial thromboplastin time (aPTT), normal prothrombin time (PT), normal platelet count and deficiency of a coagulation factor involved in the early phase of the intrinsic coagulation pathway. What is the most likely diagnosis?