Blood Clotting Disorders
Genetic and Acquired Diseases of Easy Clotting and Bleeding
Once in a while, a person may have a condition where blood clot formation or bleeding occurs easily. What are the various causes of these disorders?
The blood has the ability to thicken into clots and stop a bleeding process. It allows people to live even when they suffer from bodily injury. This is made possible by a complex mechanism of proteins that form clots and breaks clots in a balanced fashion. However, like many conditions, this can be prone to abnormalities.
Normal Blood Clotting
With injury to a blood vessel, two processes occur: platelet aggregation and coagulation. Platelets are small cell fragments that clump together at a blood vessel injury site. This in turn activates the coagulation cascade, a set of chain reactions involving the activation of proteins called clotting factors. The clotting factor reactions can be thought of as two different pathways merging into one. The intrinsic pathway involves proteins that include, but are not limited to, factors XII, XI, and IX. The extrinsic pathway involves factor VII among others. Both pathways activate factor X, which enters the common pathway where prothrombin is converted to thrombin and fibrinogen is converted to fibrin, the material of solid clots.
Normally, these processes are balanced by those that inhibit clotting factors or break up clots. Antithrombin inactivates thrombin and the activated forms of factors XI, X, and IX. Two other proteins, protein C and protein S, help inactivate factors V and VIII. The enzyme that directly breaks up clots is plasmin, activated by tissue plasminogen activator and urokinase.
These two sets of processes are in balance between and during bleeding episodes. An abnormality in a single protein on either side can shift the blood towards forming clots easily (thrombotic disorders) or bleeding easily.
Thrombotic Disorders
A genetic defect causing a deficiency in antithrombin, protein C, and protein S can lead to easy clot formation because these proteins are not present to inactivate clotting factors. There are also two gene mutations that can create hypercoagulable states. Factor V Leiden is a mutation that makes it hard for factor V to be broken down, so clots easily form because factor V lingers in the blood much longer. A mutation in prothrombin called the prothrombin 20210 mutation creates higher than normal levels of the clot-forming prothrombin.
Other causes of easy clotting can be acquired in one's lifetime. Some people may develop antiphospholipid antibodies, such as anticardiolipin antibodies or lupus anticoagulant. They bind to proteins that normally prevent excessive coagulation. When this happens, clotting ensues because the proteins are no longer protecting against this process. The person may also be hypercoagulable if he or she has excessive levels of homocysteine in the blood (hyperhomocysteinemia), which can occur with genetic abnormalities or deficiencies in folate, vitamin B12, or vitamin B6.
In thrombotic disorders, clots can form within the veins in the leg (deep vein thrombosis) which can break off, travel through the blood, and get stuck in the lung's circulation (pulmonary embolism). They can also occur in other parts of the circulatory system, such as the portal vein going into the liver or the coronary arteries of the heart. Treatment is related to the location of the clot, but in several cases, anticoagulation with the blood-thinning medications heparin and warfarin is necessary.
Bleeding Disorders
Genetic mutations resulting in deficiencies of clotting factors can lead to a tendency to bleed. The classic examples are a deficiency in factor VIII, called hemophilia A, and a deficiency in factor IX, called hemophilia B. Clotting factor deficiencies can also be acquired. For example, the blood-thinning medication warfarin inhibits production of factors II, VII, IX, and X, and if there is too much of this drug in the system, the result may be a critical tendency to bleed.
With platelets, various conditions can drop the platelet count, and critically low levels can lead to easy bleeding, often in the form of easy bruising. One genetic condition can cause platelets to not clump as well as they should. Von Willebrand's disease is a deficiency in von Willebrand factor, a protein necessary for platelet clumping.
With these conditions, bleeding can occur in various locations. Treatment depends on the condition, but it often involves addressing the deficiency. This is done with transfusion of platelets or fresh frozen plasma, which contain the various clotting factors. Injections of individual clotting factors are also an option.
Final Words
The preceding information is provided as an overview of how thrombotic disorders occur with deficient inhibitors or abundant clotting factors and how bleeding disorders occur with deficient clotting factors. The causes mentioned here do not comprise a complete list. Those who may have one of these conditions are encouraged to speak with their doctor for more information.
