What is a bleeding disorder?
A bleeding disorder is a tendency to bruise easily or bleed excessively or for prolonged periods. It may be the result of certain genes that an individual has inherited or caused by conditions or factors that develop within a person's lifetime (acquired).
Normally, blood remains in the circulatory system inside the blood vessels. When there is an injury to a blood vessel or tissue and bleeding begins, the body stops the blood loss through a complex clotting process called hemostasis. During primary hemostasis, the injured blood vessel constricts to reduce blood flow and small cell fragments in the blood called platelets adhere to the injury site, clump together (aggregate) with other platelets, and release chemical compounds that stimulate further aggregation of other platelets to form a loose platelet plug. At the same time, activated platelets support the activation of the coagulation cascade, a series of steps that involves the sequential activation of proteins in the blood called clotting factors (coagulation factors). This secondary hemostasis process results in the formation of strands of fibrin that weave through the loose platelet plug and compress to form a stable blood clot. This barrier prevents additional blood loss and remains in place until the injured area has healed.
Hemostasis is a dynamic process, though, so once a clot is formed, certain factors are activated to slow the clotting process. They eventually begin to dissolve the clot in a process called fibrinolysis so that the clot is removed when the injury site is healed. In normal, healthy individuals, this balance between clot formation and dissolution ensures that bleeding does not become excessive and that clots are removed once they are no longer needed.
Each component of primary and secondary hemostasis must be present, activated at the right time, and functioning properly for adequate clotting. If there are insufficient platelets or coagulation factors, or if platelets or coagulation factors are not functioning normally, a stable clot may not form and a person may be at an increased risk of excessive bleeding.
Bleeding disorders occur when something goes wrong with the clotting process, for example when a component is missing, deficient, or not functioning properly. Disorders may involve problems with the structure of the blood vessels, the production or function of platelets or one or more of the coagulation factors, and/or the integrity and stability of the blood clot. Inherited bleeding disorders are rare and tend to be caused by a deficiency or dysfunction of a single coagulation factor or clotting component. Acquired bleeding disorders, those with no genetic component, are varied and occur more frequently than inherited disorders.