The
causes for development of AHIA are many and they all
relate to factors that cause the immune system to be
tricked into thinking that the red blood cells are no
longer part of the body. The immune system suddenly
sees the red cell as a foreign element and proceeds to
destroy it, much in the same way it would destroy a
bacteria or virus. We know that certain drugs
(particularly antibiotics containing sulfur); vaccines,
viral infections, bacterial infections, cancer and
others have all been related to the development of AHIA.
Why one patient gets AHIA while another does not is
still a mystery.
Consequences of AHIA:
Red
blood cells are needed to transport oxygen throughout
the body. When they are destroyed, the body can not get
enough oxygen and the following symptoms are seen:
Weakness Lethargy
Confusion Rapid Respiration
Lack of Appetite
Collapse Death
If the
red cells are destroyed within the blood vessels
(intravascular hemolysis), the hemoglobin (pigment in
the red cell) will be filtered through the kidney and
may turn the urine a port wine color. The hemoglobin is
toxic to the kidneys and may lead to kidney failure.
Hemoglobin is broken down in the liver and may lead to
jaundice (yellow pigmentation of the skin and mucus
membranes) if the liver is unable to deal with the large
quantity of hemoglobin produced by the dying red cells.
The breakdown of the red cells causes an inflammatory
response in the body, which may lead to fever.
Diagnosis of AHIA:
There
are a number of blood tests that we use to help diagnose
AHIA. The first is the “Coombs” test, which checks to
see if there are antibodies directed against the red
cells. If this is positive, then the diagnosis is
confirmed. However, if it is negative, the pet may
still have AHIA. Additional tests that are helpful are
part of an immune panel that checks for aberrations in
the immune system. Sometimes, we have to reach the
diagnosis by elimination of other possibilities.
Goals of Therapy and treatment:
Treatment for AHIA involves the following:
-
Trying to determine and eliminate the causal factor
(remove drugs, treat infections, remove cancer
etc).
-
Suppress the immune system’s activity to stop the
destructive process.
-
Replace blood cells if the anemia is severe
-
Provide materials to help rebuild the blood cells
The
first drug we use is Prednisone
(a form of cortisone). Given at high doses, this drug
will inhibit the immune system’s ability to kill the red
cells. Often times, we must add additional drugs such
as Cyclophosphamide, Azathiaprine or
Cyclosporine, all of which are very potent
drugs. All of these drugs have side effects that are
fairly common. In general, the positive, life saving
effects of the drugs outweigh the negative side effects,
however, these patients must be monitored carefully both
at home and through laboratory tests.
For
patients that are severely anemic, blood transfusions
may be necessary to provide red cells until their body
can produce more. Transfusions can be life saving, but
they do pose some risk of adverse reaction where the
body rejects the new cells.
Because
prednisone can cause stomach ulcers, we typically
administer drugs to help protect the stomach during the
course of treatment.
Vitamin
and iron supplements are given to provide the building
blocks for the new red cells.
