Thrombocytopenia (Low Platelet Count) (cont.)
What causes thrombocytopenia?
Low platelet counts, thrombocytopenia, can be caused by a variety of reasons.
In general, they can be divided into:
- decreased platelet production,
- increased platelet destruction or consumption, or
- increased splenic sequestration (capturing of circulating platelets in
the spleen).
Some of the most common and important causes or thrombocytopenia are outlined
below.
Decreased platelet production
Decreased platelet production is usually related to a bone marrow problem
(agranulocytosis). In most of these conditions,
red blood cell and white blood cell productions may also be affected.
- Viral infections affecting the marrow for example:
- Aplastic anemia is a general term used when the bone
marrow fails to produce any blood cells (red cells, white cells, and platelets), also called
pancytopenia. This can
be caused by some viral infections (parvovirus or HIV), medications (gold,
chloramphenicol, Dilantin, valproate (Depacon), or
radiation, or rarely, it can be
congenital (Fanconi's anemia).
- Chemotherapy drugs frequently cause bone marrow suppression resulting in
thrombocytopenia.
- Some drugs other than chemotherapy can suppress platelet production, such
as thiazide diuretics.
- Cancers of the bone marrow and blood (leukemia) or
cancers of the lymph
nodes (lymphoma) can cause various degrees of thrombocytopenia.
- Cancers from other organs can sometimes infiltrate
(invade) the bone marrow
and result in impaired production of platelets.
- Long term alcohol can cause direct
toxicity of the bone marrow.
- Deficiency of vitamin B12 and
folic acid can result in low platelet
production by the bone marrow.
Increased platelet destruction or consumption
Increased platelet destruction or consumption can be
seen a number of medical conditions. They can be divided into immune related and non-immune related
causes.
Many medications can cause low platelet count by
causing immunologic reaction against platelets, called drug-induced
thrombocytopenia. Some examples may include:
Splenic sequestration
Splenic sequestration can also lead to low platelet counts as a result of
enlargement of the spleen for a variety of reasons. When the spleen enlarges, it
can retain (sequester) more than the usual amount of platelets. Common causes of
thrombocytopenia due to splenic enlargement may include advanced
liver disease (cirrhosis, for example, from chronic
hepatitis B or
C) and blood cancers
(leukemias or lymphomas).
- Dilutional thrombocytopenia can result from severe bleeding and transfusion
of several units transfused red blood cells in a short time.
- Pseudothrombocytopenia (false thrombocytopenia) is also
one of a commonly encountered condition where the number of platelets seen on a
complete blood count analysis (CBC) may falsely appear low because of the clumping of platelets
together. This can lead to a smaller number of platelets seen throughout the
slide reviewed by the technician. If this is suspected, the blood can be redrawn
in a tube with a material that prevents clumping of platelets for repeat
analysis.
- Thrombocytopenia can also be present at birth, called
neonatal thrombocytopenia. Most of these cases can be caused by processes
similar to above, although, they are occasionally related to rare genetic
conditions.
Next: What are the symptoms of thrombocytopenia? »
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