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Category: Hematology Articles

Protein S Deficiency ?>

Protein S Deficiency

Protein S Deficiency Introduction Background In 1979, researchers in Seattle, Wash, first discovered protein S and arbitrarily named it after the city of its discovery. Protein S is a vitamin K–dependent anticoagulant protein. Its major function is as a cofactor to facilitate the action of activated protein C (APC) on its substrates, activated factor V (FVa) and activated factor VIII (FVIIIa). Protein S deficiencies are associated with thrombosis. Protein S deficiency may be hereditary or acquired, the latter is usually…

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Protein C Deficiency ?>

Protein C Deficiency

Protein C Deficiency Introduction Background Protein C deficiency, a deficiency of the anticoagulant protein C, is associated with a variably increased risk of thrombosis. In the rare inherited homozygous or compound heterozygous state, protein C deficiency is associated with severe life-threatening neonatal purpura fulminans or massive venous thrombosis. The inherited heterozygous state of protein C deficiency most frequently is associated with deep venous thrombosis of the lower limb but also may manifest in other venous locations. A significant percentage of…

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Platelet Disorders ?>

Platelet Disorders

Platelet Disorders Introduction Background The hemostatic system consists of platelets, coagulation factors, and the endothelial cells lining the blood vessels. The platelets arise from the cytoplasmic fragmentation of megakaryocytes in the bone marrow and circulate in blood as disk-shaped anucleate particles. Under normal circumstances, the resistance of the endothelial cell lining to interactions with platelets and coagulation factors prevents thrombosis. When endothelial continuity is disrupted and the underlying matrix is exposed, a coordinated series of events are set in motion…

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Factor VII ?>

Factor VII

Factor VII Introduction Background Blood coagulation is a series of reactions in which plasma zymogens are converted into active enzymes. The final event of these reactions is the formation of an insoluble fibrin clot. These coagulant reactions are regulated by a number of stimulatory and inhibitory mechanisms. Thus, coagulation is a finely regulated system that maintains blood in a fluid phase but can rapidly respond to injury for the formation of clots. Factor VII is a vitamin K–dependent serine protease…

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Factor VIII ?>

Factor VIII

Factor VIII Introduction Background The hemostatic system, consisting of the blood vessels and their content, blood, plays a crucial role in human survival. The importance of the plasma coagulation system in protecting life by preventing further blood loss following transection of a blood vessel is well recognized. Blood is usually maintained in a fluid state, without evidence of bleeding or clotting. The presence of an X-linked pattern of inheritance of a bleeding diathesis in families, referred to as hemophilia, has…

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Factor II ?>

Factor II

Factor II Introduction Background Clotting factor II, or prothrombin, is a vitamin K–dependent proenzyme that functions in the blood coagulation cascade. Factor II deficiency is a rare, inherited or acquired bleeding disorder. In 1947, Quick and colleagues were the first to describe a deficiency of factor II1; in 1969, Shapiro and colleagues were the first to report a structural prothrombin abnormality.2