Coagulation disorders occur when the blood does not form clots properly. Blood clots are clumps of different types of blood cells and clotting factors that stop bleeding after an injury. Patients with coagulation disorders may develop too many blood clots that eventually block blood vessels, while others may not clot enough and have excessive bleeding in the body. Both of these conditions range from mild to severe and life threatening.
The process of blood clotting is called coagulation or hemostasis. There are three major phases of coagulation: narrowing of blood vessels, activation of platelets, and activation of blood clotting factors.
Phase 1: When a blood vessel (vein or artery) becomes injured, it narrows to slow blood flow so that clotting can begin. At the same time, the blood that has leaked outside of the injured blood vessel presses against the vessel to help prevent further blood loss.
Phase 2: Blood cells called platelets are activated to move towards the site of injury. The platelets produce a substance called von Willebrand factor, which has a major role in blood coagulation and helps platelets stick to the blood vessel's walls.
Phase 3: Once platelets reach the site of injury, a series of reactions by enzymes called "coagulation factors" lead to the activation of a protein called thrombin. This protein converts a blood clotting factor, called fibrinogen, into long strands that form a net around the platelets and blood cells. This net helps trap more platelets to form a blood clot.
The blood clot, also called a thrombus, is a temporary plug to control bleeding. Once the platelets are clumped together, they change in shape from round to spiny.
Sometimes blood clots are visible, and they appear as bruises on the skin.
Once the blood vessel is healed, other blood factors are released to destroy the clot. The clot is then dissolved into the blood.
Abnormalities in the clotting process can lead to coagulation disorders, such as thrombocytopenia or hemophilia. These disorders may be long-term inherited conditions or temporary conditions that are triggered by surgery, severe injuries, or other medical conditions (e.g. arterial fibrillation or heart attack).
When there is too much clotting, small blood vessels can become clogged. When a patient's vein is blocked with a clot, the condition is called venous thrombosis. As a result of excessive clotting, blood flow is limited or completely blocked through the blood vessel. Depending on where the blockage occurs, the condition can be potentially fatal. For instance, if arteries in the heart are blocked, it may lead to a heart attack.
In some cases, a blood clot may form and travel through the blood vessels. Eventually, this free-floating clot may become too large to pass through a vein or artery, and the clot may become lodged in the vessel.
When blood does not clot effectively, as occurs with certain conditions, such as hemophilia or von Willebrand disease, even a minor injury to a blood vessel may lead to serious blood loss.
Most coagulation disorders affect multiple veins and arteries. The veins in the legs are the most commonly affected blood vessels. Blood clots in the veins of the legs are a potentially life-threatening condition called deep vein thrombosis (DVT). DVT is considered a dangerous condition because small pieces of the blood clot can break off and travel to the heart, lungs, or brain. If a clot blocks an artery in the lungs, it is called a pulmonary embolism. If a blood vessel to the brain becomes blocked, it is called a stroke.
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