hematology and oncology
Hemophilia
Key Points
Hemophilias are X-linked recessive disorders of coagulation. Hemophilia A (about 80% of patients) involves factor VIII deficiency, and hemophilia B involvesfactor IXdeficiency. Patients bleed into tissues (eg, hemarthroses, muscle hematomas, retroperitoneal hemorrhage) following minimal trauma; fatal intracranial hemorrhage may occur. The partial thromboplastin time is prolonged, but the prothrombin time and platelet count are normal; factor VIII and IX assays determine the type and severity of the hemophilia. Patients with bleeding or in whom bleeding is anticipated (eg, before surgery or dental extraction) are given replacement factor, preferably using a recombinant product; dose depends on the circumstances. About 30% of patients with severe hemophilia A who require repeated factor VIII infusions develop antibodies to factor VIII. 