Snapshot A 4-year-old boy is brought into the emergency room after he is pushed on the playground. After falling to his knees, he develops grossly swollen and painful joints bilaterally, where the trauma occurred. Aspiration of the knee reveals frank blood. Platelet count and PT are normal. However, PTT is increased. Introduction Hereditary deficiencies in coagulation factors Intrinsic pathway coagulation defects hemophilia A deficiency of factor VIII hemophilia B deficiency of factor IX both lead to inadequate generation of thrombin Genetics both X-linked recessive Epidemiology almost exclusively in males Hemophilia A and B are clinically indistinguishable Presentation Symptoms are similar in both hemophilia A and B spontaneous bleeding or bleeding following trauma or surgery hemoarthroses bleeding into joints easy bruising Physical exam swollen and painful joints Evaluation ↑ PTT corrected with mixing studies indicates a factor deficiency normal PT normal bleeding time most specific test functional assay for factor VIII or IX Differential Diagnosis DIC von Willebrand disease Platelet function disorders Treatment Mild cases DDAVP for hemophilia A increases endogenous factor VIII Severe cases factor VIII or IX replacement Inhibitor cases immune tolerance induction Prognosis, Prevention, and Complications Prognosis normal mortality Complications musculoskeletal complications synovitis arthropathy