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Hematology Hemophilia A and B Diagnosis Factor VIII (hemophilia A) and factor IX (hemophilia B) deficiencies o X-linked disorders seen almost exclusively in men . consider in patients with a personal or family history of spontaneous, excessive posttraumatic or unexpected surgical bleeding Up to one third of patients with hemophilia A may develop factor VIll inhibitor antibody. The presence and quantity of inhibitor are measured with the Bethesda assay, and the level of the assay determines therapy. Testing The PT is normal and the aPTT is prolonged in hemophilia A and B. The results of a mixing study will normalize in a patient with a factor deflciency but will remain abnormal if an inhibitor is present. Treatment Factor VIII or factor IX replacement is indicated for patients with hemophilia A or B, respectively, and severe bleeding or hemarthrosis. Patients with mild hemophilia A should be given desmopressin for acute bleeding or before undergoing minimally invasive procedures (e.g., dental procedures). Prophylactic factor replacement has been proven to reduce the incidence of arthropathy in patients with severe hemophilia. If factor VIII inhibitor is present in low quantities (<5 Bethesda units), factor VIII replacement can overcome the inhibitor and control bleeding. TESTYOURSELF A 57 year old man has a large left sided ecchymosis. The hemoglobin concentration is 8 g/dl, platelet count is 220,000/pL, PT is 12 s, and aPTT is 67 s. The abnormal aPTT does not correct with a mixing study. ANSWER: For diagnosis, choose acquired factor VIII inhibitor. von Willebrand Disease Diagnosis The most common inherited bleeding disorder is vWD, an autosomal codominant disorder vWF adheres platelets to injured vessels and acts as a carrier for factor VIII. Clinically, patients have mild-to-moderate bleeding evidenced by nosebleeds, heavy menstrual flow, gingival bleeding, easy bruising, and bleeding associated with surgery or trauma. Secondary hemostatic dysfunction can occur because of concomitantly low factor VIII levels in vWD. This distinction is important for treatment purposes. 211