Hemophilia
Jeanne M. Lusher MD1
Indira Warrier MD2
1 Director, Division of Hematology/Oncology, Children's Hospital of Michigan, and Marion I. Barnhart Hemostasis Research Professor, Wayne State University School of Medicine
2 Associate Hematologist, Children's Hospital of Michigan, and Associate Professor of Pediatrics, Wayne State University School of Medicine
Hemophilia is a hereditary bleeding disorder characterized by Factor VIII (F-VIII) or Factor IX (F-IX) deficiency, bleeding into joints and soft tissues, and an X-linked mode of inheritance. Approximately one third of new cases occur as spontaneous mutations, with no family history of hemophilia. The incidence of hemophilia is about one per 20 000 persons, and one per 10 000 males.
DIAGNOSIS
Hemophilia A (characterized by F-VIII deficiency) and hemophilia B (characterized by F-IX deficiency) are clinically indistinguishable. Both affect males almost exclusively; both have the same type of bleeding; and, if the usual coagulation screening tests are performed, both are characterized by a prolonged partial thromboplastin time and normal prothrombin time. The template bleeding time is usually normal; this is expected, because the bleeding time is a reflection of platelet numbers, platelet function, capillary integrity, and von Willebrand factor activity, all of which are normal in the case of hemophilia. Hemophilia A and hemophilia B can be separated by assaying F-VIII and F-IX. Because neither F-VIII nor F-IX crosses the placenta, the diagnosis can be made at birth by obtaining a cord blood sample for assay.
CARRIER DETECTION AND PRENATAL DIAGNOSIS
Carriers of the hemophilia gene may be "obligate" carriers, in the sense that the family pedigree indicates that a particular female must be carrying the gene for F-VIII (or F-IX) deficiency.
