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1. OVERVIEW OF HEMOPHILIA A
1.1. PATHOPHYSIOLOGY
Hemophilia A is an X linked recessive bleeding disorder (Figure 1) characterized by congenital
underproduction or dysfunction of blood coagulation factor VIII (FVIII). FVIII, which is usually
produced in liver sinusoidal cells and endothelial cells outside the liver throughout the body, is
a component of the intrinsic pathway in the coagulation cascade and essential for promoting
clot formation. It is a cofactor for activated factor IX (FIXa) that forms a complex activating
factor X (FXa), which in turn cleaves prothrombin to generate thrombin. Hemophilia A results
from mutations or defects in the gene that encodes FVIII. Due to the fact that hemophilia A is
passed along by X linked recessive inheritance, the vast majority (approximately 90%) of
identified patients are males (WFH. 2016).
Parents Unaffected Carrier
father (XY) mother(XX)
+
Children
Unaffected Carrier Affected Unaffected
son (XY) daughter (XX) son (XY) daughter (XX)
Parents Affected Unaffected
father (XY) + mother (XX)
Children
Unaffected Carrier Affected Carrier
son (XY) daughter (XX) son (XY) daughter (XX)
Figure 1: Hemophilia A X-linked recessive inheritance
Hemophilia A results in a lifelong bleeding tendency and is a serious chronic disease that can
be fatal. Some patients who are born with normal FVIII develop autoantibodies directed
against FVIII.
HEMLIBRA Monograph-Non-inhibitors | 01
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HEMLIBRA Monograph-Non-inhibitors | 01