Now that we've discussed Fanconi
anemia as a genetic cause of aplastic anemia,
let's look at some of the
other causes of aplastic anemia.
The first is medications.
These can be toxic to the bone marrow and can
damage the pluripotent hematopoeitic stem cells
before they differentiate to committed stem cells.
The onset of drug-induced aplastic
anemia is variable and can be insidious.
This can occur days after the initiation of the
medication up to months after the start of a new drug.
The average time is about 6 1/2
weeks after starting a medication.
It typically starts with neutropenia
which is the low white blood cells
followed by thrombocytopenia
which is low platelets.
Finally anemia develops and this happens slowly
due to that longer lifespan of the red blood cell.
Clinical features of drug-induced aplastic anemia depend
on the degree to which each cell line is suppressed.
Medication-induced aplastic anemia is one of
the few life threatening reactions to medications.
Common drug classes
include cytotoxic chemotherapy
We know this is a medication
but this is also a toxin.
Chemotherapy is effective in killing off
cancerous cells but the chemical sometimes
ends up harming the healthy stem
cells found in the bone marrow.
In fact, chemotherapy can cause blood cell counts
to fall in the first week after starting treatment.
This reduces the number of red cells,
white cells and platelets in the body.
Thankfully this reduction is usually
temporary and it should improve
after the chemotherapy has
been successfully completed.
The next is certain medications that we used to treat
rheumatoid arthritis, and certain antibiotics.
To stop the aplastic anemia caused by a medication,
the patient will need to stop the medication, if able.
Remember this isn't always possible especially if the
medication is being used to manage a serious condition.
The patient can also receive a blood
transfusion to replace the components of the blood
that are not being made by the marrow.
The prognosis is similar when caused by
medications as when aplastic anemia is idiopathic.
These patients usually respond well to
immunosuppressive therapy and stem cell transplantation.
Aplastic anemia can also
be caused by viral infections.
It is thought of as a response to the persistent
inflammatory feedback to the hematopoietis system
which makes it difficult for the
bone marrow to function normally.
Viruses that have been linked to the
development of aplastic anemia include
hepatitis, the Epstein-Barr
virus and cytomegalovirus.
In addition, Parvovirus B19
and HIV have also been linked.
Both the virus in itself can ensue this immune
response and this can have a tremendous impact
on the hematopoeitic process
resulting in aplastic anemia.
How about aplastic anemia in pregnancy?
Well a woman who has aplastic
anemia prior to becoming pregnant
will typically have a worsening of
her symptoms during her pregnancy
and some women will develop
aplastic anemia while pregnant
which is thought of as a
sort of autoimmune reaction.
There is significant maternal and neonatal morbidity
and mortality in patients with aplastic anemia
These women have complicated
obstetric and anaesthetic management
and will likely be managed by a high
risk maternal fetal medicine specialist
These women are at high risk for
hemorrhage due their thrombocytopenia
and up to 75% of these patients require
a blood transfusion during or after delivery.
The platelet count can also be too
low to perform a safe cesarean delivery.
Due to their neutropenic state, these women
are at an increased risk for infections and sepsis.
Aplastic anemia is managed in the
same way as a non-pregnant patient
although there are some
additional potential risks.
And immunosuppressants, this
can interfere with breastfeeding
and these women may need
to formula feed their babies.
They can also receive blood
transfusions and stem cell transplant.
Chemotherapy is unique as it fits into the medication
category and it also fits into the toxin category
because it's a cellularly toxic medication.
Some patients with cancer will
also receive radiation therapy
and this can also damage the
healthy cells in the bone marrow.
This usually improves once
the therapy is completed.
Certain chemicals including pesticides, insecticides
and benzene which is an ingredient in gasoline
have been implicated and
causing aplastic anemia.
With elimination of the exposure to these
chemicals, aplastic anemia usually resolves.