Autoimmune hemolytic anemia (AHIA) is a serious disease in which the body’s immune system destroys the red blood cells. The name of this disease is a bit complicated but if we take each word by itself, it becomes more understandable. Autoimmune means that the body’s own immune system is at the root or cause of the disease. Hemolytic, means destruction of red blood cells. Anemia refers to an inadequate number of red cells in the blood.
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:
- Rapid Respiration
- Lack of Appetite
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 and other immune suppressants, 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.
It is important to understand that our treatment may not cure the disease, but instead, may keep it in remission. Most pets require treatment for a minimum of 6 months during which time we try to wean them slowly off the life saving drugs. In some cases, drugs are not enough to control the disease and we may have to surgically remove the spleen because this organ is the site where the majority of the red cell destruction takes place. Overall, 75% of pets with AHIA can go on to live a normal life.
Unfortunately, some patients will die from this disease despite even the most aggressive treatment. It is difficult to predict who will survive and who will succumb to the disease, but a positive response to initial therapy makes for a better prognosis than a pet that does not respond initially. Each time a pet comes out of remission (the anemia begins again) the prognosis gets more guarded.