A 2-year-old boy bleeds excessively from minor injuries and has previously had bleeding gums. The maternal grandfather has a bleeding disorder. The child's physical examination shows slight tenderness of his knee with fluid accumulation in the knee joint. You suspect this patient is deficient in which coagulation factor?
High-Yield Explanation
A young man with a bleeding disorder and a history of bleeding disorders in the males of his family would lead one to suspect hemophilia A (a deficiency of factor VIII.) The physical examination suggests bleeding into the knee joint, which is frequently seen in hemophilia A.