at Morris Animal Foundation
Meisha, a lab/terrier/spaniel mix, was 3 years old when she was diagnosed with autoimmune hemolytic anemia (AIHA), also known as immune-mediated hemolytic anemia (IMHA), in January of 1992. Her doctor said that if she survived the initial crisis she might live 2 or 3 more years. Meisha lived for 9 years & 10 months after her AIHA diagnosis. She died on November 23, 2001. The visual autopsy indicated that perhaps she had died of cancer, however the results of the tissue autopsy revealed she died amyloidosis probably caused by the long-standing AIHA. This site is dedicated to her and all the other dogs and their families who struggle with autoimmune hemolytic anemia.
Lets define the terms of the disease one at a time. "Autoimmune" literally means the immunity against the self."Hemolytic" is the destruction of red blood cells. "Anemia" is a clinical sign, not a disease. Anemia is defined as a decrease in the number of red blood cells (RBC's) or the amount of hemoglobin, resulting in a decrease in the oxygen- carrying capacity of the blood.
In AIHA, markers called antibodies, stick to the red blood cells and cause the body to believe the red blood cells are a "foreign invader". This causes the immune system to "kick in", attack the red blood cells and destroy them. The mechanism by which the immune system mistakes the red blood cells for a "foreign invader" varies somewhat according to the cause. It usually involves adherence of the offending agent (parasite, drug or toxin) to the surface of the red blood cells. The immune system wishes to attack the offending agent, but manages to injure the red blood cells as well. When the spleen and the rest of the immune system is working to rid the body of the old, diseased or damaged red blood cells, it is doing its job properly. However, when a large percentage of the cells are affected, and they are removed faster then they are replaced, AIHA results. The destruction of red blood cells often leaves recognizable cellular debris in the blood stream. In particular, a form of damaged red blood cell known as a spherocyte occurs. Finding spherocytes on a blood smear almost guarantees that some form of hemolytic anemia is occurring. Since this disorder does not stop the production of red blood cells, there are usually immature red blood cells in the bloodstream which can be detected on the blood smears as well.
The symptoms or clinical signs of AIHA can appear suddenly or they may be gradual and progressive. The signs are usually related to the lack of oxygen and manifest themselves in the form of weakness, lethargy, and an increase in the heart and respiration rate. Pale mucous membranes (gums, ears, eyelids) may be observed. The dog also may appear to be jaundice. This is due to a build up of bilirubin, one of the breakdown products of hemoglobin. Vomiting or abdominal pain may be present. Owners may note the presence of blood in the urine or stool Also an increase in temperature may be observed in some dogs. A diagnosis of AIHA is made on the basis of these clinical signs as well as a complete blood count (CBC) and other testing. A Coombís test should be performed to confirm the diagnosis. A small percentage of dogs that have AIHA will test negative on the Coombís test.
Most of the time, a specific cause for AIHA is unrecognized. Many theories exist, but the ultimate answer is "We donít know." Dr. Jean Dodds, a veterinarian studying immunology, states in her article, The Immune System and Disease Resistance, that there are four main causative factors of autoimmune diseases. Those factors are: Genetic predisposition; Hormonal influences; Infections, especially of viruses and Stress.
According to the Textbook of Veterinary Internal Medicine, the following are examples of underlying disorders and triggers of immune-mediated hemolytic anemia:
- Viral: transient or chronic persistent upper respiratory or gastrointestinal (GI) viral diseases
- Bacterial: leptospirosis, hemobartonellosis, various acute infections (e.g., abscess, pyometra, discospondylitis)
- Parasitic: babesiosis, leishmaniasis, dirofilariasis, ehrlichiosis, ancylostoma caninum
- Other emerging infectious diseases (e.g., bartonellosis), bee stings
Sulfonamides Cephalosporin Penicillin Vaccines Procainamide
Hemolymphatic: leukemias, lymphoma, multiple myeloma Solid tumors
SLE Hypothyroidism Primary and secondary immunodeficiencies
American Cocker Spaniel (one third of all cases) English Springer Spaniel Old English Sheepdog Irish Setter Poodle Dachshund
Female dogs appear slightly predisposed to AIHA/IMHA, even when spayed.
To learn how you can help fund humane canine AIHA/IMHA health studies at Morris Animal Foundation Click Here
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Links to other AIHA/IMHA sites
The Body Against Itself: Immune-Mediated Hemolytic Anemia. A Webinar presented by Morris Animal Foundation
Diagnosis of Hemolytic Anemias
Canine Autoimmune Hemolytic Anemia
Immune Mediated Hemolytic Anemia (IMHA)
Canine Immune Mediated Hemolytic Anemia
Immune-Mediated Hemolytic Anemia & Immune-Mediated Thrombocytopenia
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This page was last updated on January 7, 2015.
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