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Autoimmune Hemolytic Anemia (and "Immune Mediated Hemolytic Anemia")

General Information

Your pet's immune system provides the ability to resist and recover from disease and injury. This defense system regulates production of antibodies that aid in destruction of disease agents, such as bacteria and viruses.

In autoimmune hemolytic anemia, this defense system goes astray and attacks the animal's own body and red blood cells, causing severe, life-threatening anemia. While such disruption of the immune system may be caused by infection, cancer or other diseases, in many cases the cause is unknown. Certain drug reactions may cause autoimmune hemolytic anemia. In newborns, the disease may result from antibodies found in the first milk (colostrum) of the mother.

Important Points in Treatment

1. Autoimmune hemolytic anemia is a serious, life-threatening disease. In many cases, immediate blood transfusions are needed. Less severe cases are treated with a variety of medications. In some patients, surgical removal of the spleen or treatment with anti-cancer drugs is necessary.

2. Various laboratory tests are necessary to diagnose the condition and monitor the response to treatment. Monitoring the disease freqently is necessary early in the course of the disease. After initial recovery periodic monitoring may be needed to avoid serious relapses.

3. In some cases we are able withdraw medication and normal life continues without teatment. In other cases medications must be continued for the rest of the animals life. Relapses are common.

4. Medication must be given as directed. Call the doctor if you cannot give the medication. Watch for signs that any prescribed medication might be causing problems such as vomiting or darkening of the stool. Many of the medications used for treatment of AIHA suppress the immmune system so watching for signs of other disease occuring are important.

5. Diet: Follow the instructions checked.

____Feed the normal diet. ____A special diet is required. Feed as follows:


6. Activity: Follow the instructions checked.

____Normal activity is allowed. ____Restrict activity as follows:

Notify the Doctor if Any of the Following Occur:

* Your pet's signs recur after an apparent recovery.

* Your pet seems short of breath or weak.

Autoimmune Hemolytic Anemia (synonyms: immune-mediated anemia, AIHA)

Technical Information -Review of the disease in small animals:

etiology (cause)
- antibodies are directed against RBC membrane
- primary AIHA
- no underlying disorder
- secondary AIHA
- antibody production initiated by the presence of drugs, infections, lymphoproliferative or neoplastic disorder
- infrequently associated with immune-mediated
thrombocytopenia (destruction of platelets)

- rarely associated with systemic lupus erythematosus pathogenesis
- varies with the class of antibody:
- warm antibody (in-saline-acting autoagglutinins)
- IgG antibodies result in intravascular agglutination
- agglutination readily visible on glass slide
- warm antibody (in vivo hemolysins)
- IgG & IgM antibodies fix complement resulting in massive intravascular hemolysis

- warm antibody (an incomplete antibody)
- IgG attaches to RBC resulting in extravascular removal mostly by the spleen
- most common form of AIHA
- cold antibody (cold hemagglutinins)
- IgM has optimal activity below body temperature
- results in intravascular agglutination in the small vessels of the extremities resulting in cyanosis & necrosis of the extremities

- cold antibody (nonagglutinating antibody)
- IgG results in hemolysis at cold temperatures

 

Maggio-Price,L. { chapter 63 : Disorders of Red Blood Cells }
Handbook of Small Animal Practice
Churchill Livingstone, 1988 Pages: 725-748
Edited by Morgan RV

LifeLearn V Inc, Copyright © 1999 "Companion to Canine Practice"

Understanding Your Pet's Diagnosis

Autoimmune Hemolytic Anemia (AIHA)

Autoimmune hemolytic anemia is a disease in which the body attacks its own red blood cells. In dogs with AIHA, red blood cells are still being manufactured in the bone marrow, but once released into the circulation they have a shorter-than-normal life span since they are constantly being attacked and destroyed by abnormal antibodies in the blood. Antibodies are normally formed by the dog's immune system when needed to destroy invading bacterial or viral signs. However, with AIHA, the dog's immune system is not working normally and sees its own red blood cells as foreign, and therefore produces antibodies to destroy them.

A second abnormality often seen in AIHA is a decreased number of platelets. Low numbers of platelets is called thrombocytopenia. Platelets are tiny structures which circulate within the bloodstream and function in the formation of clots when vessels are cut or broken. Over the course of a day, many of the body's small vessels normally break and the platelets clot the blood so no bleeding occurs. A simple bruise is nothing more than a collection of broken vessels which allowed some blood to spill into and discolor the tissue. When low platelet numbers are diagnosed, clotting does not occur correctly. AIHA dogs are, therefore, similar to human hemophiliacs. Uncontrolled bleeding further decreases the number of red blood cells caused by the abnormal antibodies.

What are the symptoms?
A dog suffering with AIHA will have a lower-than-normal number of red blood cells within the blood. This is termed anemia. The lips, gums and eye margins will appear pale (or yellow in the later stages of the disease) and not the normal pink to red color. Commonly the dog will be tired and lethargic as there are not enough red blood cells to carry oxygen to the tissues. Fainting commonly occurs due to low oxygen levels in the brain.

As the red blood cells are being destroyed, hemoglobin (the oxygen carrier molecule of red blood cells) builds up to high levels within the body. The liver attempts to break it down and remove it. Elevated levels of the breakdown products causes a yellowish color to the skin and membranes that we refer to as jaundice. The urine may contain hemoglobin and appear dark or tea-colored. Additionally, the heart beats much more rapidly to pump the thinner blood faster through the tissue. This is an attempt to compensate for low oxygen levels.

If the platelets are also low in number, bleeding from the nose or blood in the stool may be seen.

What are the risks?
AIHA is serious and left untreated usually results in death. An animal that is anemic will try to compensate by pumping more blood. This can overload the heart, causing it to fail. If the animal is cut, it typically takes much longer for the bleeding to stop.

What is the management?
Most dogs with AIHA will respond to steroid therapy. The steroid prednisone has been widely used to treat AIHA. Drug therapy may be required for months to years. Prednisone suppresses the immune system, helping to prevent red blood cell destruction. Blood transfusions may be required in the critically anemic dog. Thankfully, a portion of these cases may recover and no longer need therapy.

The information on this page was obtained from the site www.peteducation.com