What Causes Thrombotic Thrombocytopenic Purpura?
A lack of activity in the ADAMTS13 enzyme (a type of
protein in the blood) causes thrombotic thrombocytopenic purpura (TPP). The
ADAMTS13 gene controls the enzyme, which is involved in blood clotting.
Not having enough enzyme activity causes platelets
to clump together, forming blood clots. In TTP, when blood clots form, there
are fewer platelets in the blood. This can cause bleeding into the skin
(purpura), drawn-out bleeding from cuts, and internal bleeding. It also causes
small blood clots to form suddenly throughout the body, including in the brain
and kidneys.
TTP also can cause red blood cells to break apart
faster than the body can replace them. This leads to
hemolytic
anemia.
Inherited Thrombotic Thrombocytopenic Purpura
In the inherited form of TTP, changes in the
ADAMTS13 gene affect the enzymes function. The gene doesnt prompt
the body to make a normal ADAMTS13 enzyme. As a result, enzyme activity is
lacking or is altered.
Inherited means that the condition is
passed from parents to children. In inherited TTP, a person is born with two
copies of the altered geneone from each parent. Most often, the parents
each have one copy of the altered gene, but have no signs or symptoms of the
disorder.
Acquired Thrombotic Thrombocytopenic Purpura
In the acquired type of TTP, the ADAMTS13 gene
isnt changed. Instead, the body makes proteins called antibodies that
block the ADAMTS13 enzymes activity.
Acquired means you arent born with
the condition, but you develop it.
Triggers for Thrombotic Thrombocytopenic
Purpura
What triggers TTP isnt known, but some factors
may play a role. These include:
- Diseases and conditions such as pregnancy,
cancer, HIV, infection, and lupus
- Medical procedures such as surgery and bone
marrow transplant
- Medicines such as chemotherapy, ticlopidine,
clopidogrel, cyclosporine A, and hormone replacement therapy and estrogens
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