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INTRODUCTION

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Hemophilias are bleeding disorders due to deficiency in one of the factors present in the clotting cascade.1,2 The most common factor abnormalities are of factor VIII (hemophilia A) or factor IX (hemophilia B). von Willebrand's disease is a related defect of the von Willebrand factor.3

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These hereditary bleeding disorders typically appear early in life, and adult patients will usually be able to relate a history of a bleeding problem. However, patients with mild forms of inherited disease may be unaware of a bleeding disorder until stressed by significant trauma or development of another hemostatic problem.

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Systemic bleeding disorders should be suspected in patients with severe bleeding related to trivial trauma or minor surgery, or spontaneous bleeding, particularly when the bleeding occurs in joints or muscle. Unusual bleeding or bruising at multiple areas should also raise concern about a coagulopathy. Medications can be responsible for unmasking a mild bleeding diathesis.

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The pattern of bleeding can suggest a likely cause. Patients with easy bruising, gingival bleeding, epistaxis, hematuria, GI bleeding, or heavy menses are more likely to have a deficiency or dysfunction of the platelets. Conversely, patients with spontaneous deep bruises, hemarthrosis, retroperitoneal bleeding, or intracranial bleeding are more likely to have a coagulation factor deficiency. In factor-deficient patients, bleeding associated with trauma may be delayed, due to inadequate fibrin clot formation that inadequately stabilizes the initial platelet thrombus. Patients with von Willebrand's disease may present with features of both platelet and clotting factor problems.

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HEMOPHILIA

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EPIDEMIOLOGY

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The genes that encode factors VIII and IX are located on the long arm of the X chromosome. A genetic mutation in the factor VIII gene produces hemophilia A, occurring in about 1 in 5000 male births in the United States. A mutation in the factor IX gene causes hemophilia B, affecting approximately 1 in 25,000 male births in the United States. Together, these two forms of hemophilia make up about 99% of patients with inherited coagulation factor deficiencies. Hemophilia A and B are clinically indistinguishable from each other, and specific factor testing is required to identify the type.

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Because hemophilia A and B are X-linked disorders, hemophilia is overwhelmingly a disease of men, with women typically being asymptomatic carriers. Only rarely do women have severe disease. While these disorders are genetic and usually inherited, a family history of bleeding may be absent because approximately one third of new cases of hemophilia arise from a spontaneous gene mutation.

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PATHOPHYSIOLOGY

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Bleeding manifestations in patients with all forms of hemophilia are directly attribuTable to the decreased plasma activity levels of either factor VIII or IX (Table 235-1). Those with factor activity levels of 0.3 to 0.4 IU/mL (30% to 40% of normal) may never be aware that they have ...

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