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The Clotting Process
 Clotting factors are proteins in the blood that control bleeding.
When a blood vessel is injured, the walls of the blood vessel contract to limit the flow of blood to the damaged area. Then, small blood cells called platelets stick to the site of injury and spread along the surface of the blood vessel to stop the bleeding. At the same time, chemical signals are released from small sacs inside the platelets that attract other cells to the area and make them clump together to form what is called a platelet plug.
On the surface of these activated platelets, many different clotting factors work together in a series of complex chemical reactions (known as the coagulation cascade) to form a fibrin clot. The clot acts like a mesh to stop the bleeding.
Coagulation factors circulate in the blood in an inactive form.
When a blood vessel is injured, the coagulation cascade is initiated
and each coagulation factor is activated in a specific order
to lead to the formation of the blood clot. Coagulation factors are
identified with Roman numerals (e.g. factor I or FI).
What are rare clotting factor deficiencies?
If any of the clotting factors is missing or is not working properly, the coagulation cascade is blocked. When this happens, the blood clot does not form and the bleeding continues longer than it should.
Deficiencies of factor VIII and factor IX are known as hemophilia A and B, respectively. Rare clotting factor deficiencies are bleeding disorders in which one of the other clotting factors (i.e. factors I, II, V, V + VIII, VII, X, XI, or XIII) is missing or not working properly. Less is known about these disorders because they are diagnosed so rarely. In fact, many have only been discovered in the last 40 years.
See Characteristics of Rare Clotting Factor Deficiencies table
Content developed by the WFH von Willebrand Disease and Rare Bleeding Disorders Committee
Last Updated June 2010 |
