Excessive clotting (thrombophilia) occurs when the blood clots too easily or excessively.
Inherited and acquired disorders can increase blood clotting.
Clots in larger blood vessels cause legs or arms to swell.
Blood levels of proteins that control clotting are measured.
People may need to be treated with anticoagulants.
(See also How Blood Clots.)
Most disorders that cause thrombophilia increase the risk of blood clot formation in veins. A few increase the risk of clot formation in both arteries and veins.
Causes of Excessive Clotting
Some of the disorders that cause thrombophilia are inherited. Many of these result from changes in the amount or function of certain proteins in the blood that control clotting. For example:
Activated protein C resistance (factor V Leiden mutation)
Deficiency of antithrombin
Deficiency of protein C
Deficiency of protein S
Prothrombin 20210 mutation (a specific mutation in the prothrombin gene that causes the body to produce excess prothrombin, a protein involved in the blood clotting process)
Elevated clotting factors VIII, IX, and XI
Other disorders that cause thrombophilia are acquired after birth. These disorders include disseminated intravascular coagulation (often occurring in people with cancer), and antiphospholipid syndrome (sometimes occurring in people with systemic lupus erythematosus), which increase the risk of clotting because of overactivation of blood clotting factors. Hyperhomocysteinemia (an abnormal elevation of homocysteine, most often caused by deficiencies of vitamin B6, vitamin B12, or folate) is a possible cause of thrombophilia.
Other factors may increase the risk of clotting along with thrombophilia. Many involve conditions that result in a person's not moving around sufficiently, causing blood to pool in the veins. Examples are paralysis, prolonged sitting (especially in confined spaces as in a car or airplane), prolonged bed rest, recent surgery, and heart attack. Heart failure, a condition in which the blood is not pumped sufficiently through the bloodstream, is a risk factor. Conditions that result in increased pressure on veins in the legs, including obesity and pregnancy, also increase risk.
Symptoms of Excessive Clotting
Most of the inherited disorders do not begin to cause an increased risk of clotting until young adulthood, although clots can form at any age.
Symptoms depend on the location of the blood clot. A blood clot in a leg (called deep vein thrombosis) causes leg pain in the calf or thigh as well as warmth, redness, and swelling in the leg. If the blood clot travels to the lungs (called pulmonary embolism), the person has shortness of breath and chest pain (often that is triggered by breathing).
After several deep vein clots have occurred, more serious swelling and skin discoloration may develop (chronic deep vein insufficiency). Sometimes, clots form in superficial leg veins (veins near the surface of the skin), causing pain and redness (superficial thrombophlebitis). Less commonly, clots may form in arm veins, abdominal veins, and veins inside the skull. The antiphospholipid syndrome may result in clots in arteries or veins.
When clots obstruct blood flow in arteries, tissues have a reduced blood supply and may be damaged or destroyed, possibly causing a heart attack or stroke. Clots in leg or arm arteries cause the leg or arm to be cold, painful, and sometimes numb.
Blood clotting disorders can cause women to have recurrent miscarriages.
Diagnosis of Excessive Clotting
Blood tests to identify the specific cause of the blood clots
Testing to identify the location of the blood clots
A person who has had at least two separate instances of a blood clot without an apparent predisposing factor may have an inherited disorder that causes thrombophilia. An inherited disorder may also be suspected if a person with an initial blood clot has a family history of blood clots. A young healthy person who develops an initial clot for no apparent reason may have an inherited disorder.
Blood tests that measure the amount or activity of different proteins that control clotting are used to identify specific inherited disorders that cause thrombophilia.
Other testing depends on where the blood clot develops. If a clot is suspected in the leg, an ultrasound is done to look for blockage in a leg vein. If a pulmonary embolism is suspected, computed tomography angiography of the lungs or a special nuclear scan of the lungs is done.
Treatment of Excessive Clotting
Anticoagulants
heparin, because warfarin can cause birth defects or severe bleeding in the newborn. People who take warfarin require frequent blood clotting testing and may need their dose adjusted to be sure the level of anticoagulation is right.
Direct oral anticoagulants (DOACs), medications that do not require frequent blood clotting tests, are effective alternatives to oral warfarin
People who have had two or more clots are especially likely to be advised to take an anticoagulant such as warfarin or a DOAC for the rest of their lives.
The inherited disorders that cause thrombophilia cannot be cured. Hyperhomocysteinemia is treated with supplements of deficient vitamins, but there is no clear evidence that treatment reduces the risk of clotting.
Other treatment depends on the location of the blood clot.
