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Thrombosis is the presence or formation of a thrombus
- a blood clot that forms within a vein or an artery.
The condition arising from clots developing in the body’s
deep veins (typically the leg and pelvic regions) is
known as Deep Vein Thrombosis, or DVT. Sometimes the
blood clot dissolves on its own, with no harm. But a
clot that prohibits adequate amounts of blood to pass
through a vein can result in necrosis, or tissue death.
Even worse, the clot could break off, travel through
the blood stream, and lodge itself in an artery in the
lungs, causing a life-threatening condition known as
pulmonary embolism (PE).
There are many reasons why these abnormal clots form.
When a person’s ability to move about is limited,
whether due to a long airplane flight (“Economy
Class Syndrome”) or confinement to a bed after
surgery, blood can pool and form clots. The use of oral
contraceptives or estrogen therapy can also cause clotting.
Genetics can have a role in the development of thrombosis.
There are several known mutations (heritable following
an autosomal dominant pattern) that interfere with the
body’s blood clotting process. The most common
is the Factor V Leiden mutation, a resistance to Protein
C, a protein that keeps the formation of blood clots
in check. Present in 5 – 7 percent of the general
population, the Factor V Leiden mutation is present
in 20 percent of more of all people with thrombosis.
Less frequently occurring mutations include Prothrombin
II, Protein C deficiency; Protein S deficiency; Antithrombin
III deficiency; Plasminogen deficiency; and Heparin
cofactor II deficiency. It is possible for a person
to have more than one of these mutations. When the Prothrombin
II mutation is present with the Factor V Leiden mutation,
the risk for DVT or PE is increased substantially.
The genetic test for Factor V Leiden and Prothrombin
II is a DNA analysis taken from a sample of blood or
cheek cells. There are also panel tests that screen
for several of the mutations described above. Testing
should be considered for: people who experience a thrombotic
event—such as a DVT or PE— before age 50
or have multiple thrombotic events; those with a family
history of thrombotic events, even if they themselves
are not experiencing symptoms; and people with a first-degree
relative who is known to have one of the thrombosis
mutations.
A person who has had a thrombotic event and, after
testing, is found to have the Factor V Leiden mutation
or any of the other thrombilia-related mutations, is
usually advised to take anticoagulant medication, such
as Coumadin. The period of time in which the medication
is taken will depend upon the specific circumstances
surrounding the thrombotic event.
Additionally, affected persons as well as family members
who have a mutation but no history or indication of
clotting disorders would be advised to take preventive
steps, such as not smoking, not taking birth control
pills, wearing support hose and stretching during long
airplane flights, and alerting their physicians if they
are scheduled for surgery or are immobilized for a long
period of time.
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