Hemophilia

The hemophilias are a group of inherited disorders characterized by decreased clotting factor activity, with prolonged and often spontaneous bleeding. Hemophilia A, or classic hemophilia, is by far the most common form of disease and results from subnormal factor VIII activity. Until recently it was thought that factor VIII was absent., but it is now recognized that material identified antigenically as factor VIII is present, although procoagulant activity is reduced. It is currently believed that factor VIII has two components. Measuring each component independently permits detection of carriers, as well as a clear delineation from von Willebrand’s disease. In the latter, procoagulant activity is present disproportionate to the amount of protein antigen, and platelet abnormalities are present as well. Hemophilia B (Christmas disease) results from deficient factor IX activity. Both hemophilias A and B are sex-linked disorders; however, the mutation rate for hemophilia A is said to be upward of 25%, one of the highest known in human disease, von Willebrand’s disease is autosomally transmitted and thus affects both sexes equally.

For reasons that remain unclear, hemophilia is rarely manifested on the first day of life, even after a difficult delivery. Factor VIII does not cross the placenta, yet the newborn with hemophilia does not experience increased bruising or unusually severe cephalhematomas. Even after circumcision, 75% of affected neonates have only mild or no bleeding; a complication from the procedure implies severe disease, defined as less than 1% normal activity. The first few months of life are usually a benign period during which the only clinical clues to the diagnosis may be exaggerated bruising from contact with crib slats. When walking – and falling – begins, excessive bruising and bleeding, particularly of the lip and tongue, are noted. Ecchymoses and soft-tissue bleeding remain common in childhood.

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