Auto Immune Hemolytic Anemia
Information for Patients and Veterinarians
What is AIHA?
hemolytic anemia (AIHA) is a disease in which the body attacks its own red
blood cells (RBC). A pet
suffering with AIHA will have a lower-than-normal number of red blood
cells within the blood. This
is termed anemia. The normal
range for the packed cell volume (PCV) or hematocrit is 37-55% (the ratio
of the volume of packed red cells to the whole blood).
classified as a “primary” immune disease. No underlying cause of the immune
destruction can be found after an exhaustive clinical and laboratory
evaluation. A “secondary”
disease is called immune-mediated hemolytic anemia (IMHA). IMHA refers to all anemias that
occur when the immune system inadvertently destroys its own blood cells
secondary to an immune attack directed against an underlying condition
such as cancer, endocarditis, heartworm or by unidentifiable causes as in
What are the Symptoms of
When a large
percentage of red blood cells (RBC) are affected, and they are removed
faster then they can be replaced, the animal shows external signs of the
The clinical signs of AIHA are usually gradual and progressive, but occasionally an apparently healthy pet suddenly collapses in an acute hemolytic crisis. The signs are usually related to lack of oxygen supply. The hemoglobin in RBC is the primary carrier of oxygen in the blood. Signs include weakness, lethargy, anorexia, and an increase in the heart rate and respiration. Heart murmurs, pale mucous membranes (gums, eyelids, etc.), and discoloration in the urine and/or stool may also be present. More severe cases also have a fever and icterus (jaundice), which is a yellow discoloration of the gums, eyes, and skin. This is due to a buildup of bilirubin, one of the breakdown products of hemoglobin.
of AIHA/IMHA is usually made on these clinical signs as well as a complete
blood count (CBC). The CBC
usually shows a regenerative anemia with spherocytes. Spherocytes are a special type of
red blood cell that develops in IMHA. The blood samples may
auto-agglutinate (clump). A
Coombs test may be done to support the diagnosis.
Why My Pet?
no one knows why an individual pet develops AIHA/IMHA. Certain breeds such as cocker
spaniels and poodles are at a higher risk than other breeds. Middle-aged female dogs are also
at a higher risk. However
immune-mediated hemolytic anemia may occur in any breed at anytime.
veterinary medical field has not discovered why an individual dog gets
AIHA/IMHA. However, evidence
suggests that recent vaccinations (DHLPP) may be associated with a higher
incidence of IMHA and so has the administration of certain medications
like sulfa-trimethoprim antibiotics.
Dogs with serious infections or cancers in their body may also
develop IMHA. The thought for
the underlying cause is that something (i.e., vaccine, cancer cells)
triggers the immune system to react and to create antibodies.
antibodies also destroy the red blood cells and sometimes also the
platelets (idiopathic thrombocytopenic purpura); and therefore, the first
sign of illness may be the anemia.
Is There a Cure?
AIHA is better
thought of as a disease that is controlled rather than cured. Medications are used to decrease
the hyperactivity of the immune system and suppress the abnormal immune
response directed against RBC.
need to be given indefinitely, but at least for several months. Most dogs are on medications for
at least 4-6 months, some much longer. Dogs that have had AIHA once are
more likely to get it again, particularly if they are weaned off medicines
very rapidly (less than 2 months).
What are the
initial drugs used are cortisone medication (prednisone,
takes approximately 5-7 days to become effective, during which time the
animal’s disease may worsen. Other cytotoxic drugs such as imuran
(azathioprine), cytoxan (cyclophosphamide), and danazol shut down the
immune cells (lymphocytes) producing antibodies and/or stop cells of the
immune system that destroy the RBC (macrophages). Other immunosuppressive therapies
such as cyclosporine administration and a host of other experimental
treatments are or have been used by various
Most pets with
AIHA/IMHA are presented for weakness and lethargy; i.e., the effects of
anemia. The pet may require a
transfusion to improve its clinical state while immunosuppressive
treatments have time to work.
The clinician may elect to give whole blood, or more commonly
packed red blood cells or synthetic hemoglobin
thromboembolism (blood clots in the lungs) results when abnormal clotting
arises from an activation of the clotting system due to inflammation and
RBC destruction. In pets with
AIHA/IMHA, several factors, including the presence of hemolysis (RBC
destruction), IV catheters, prednisone administration, and vascular stasis
contribute to the increased clotting tendency of the blood in dogs with
IMHA/AIHA. If thromboembolism
is suspected, the pet will be given doses of heparin (100-200 iu/kg of
body weight 4x per day) and possibly oxygen to reduce the labored
Side Effects from the
Prednisone and other cortisone medications are catabolic substances; pets lose muscle mass and strength. Additionally, these drugs cause increased thirst and urinations (PD/PU) by affecting kidney concentrating ability. These drugs are potentially irritating (ulcerogenic) to the gastrointestinal (GI) tract and can cause vomiting with or without GI bleeding. Pancreatitis is another potential complication associated with cortisone and aziothioprine administration.
instances, the cytotoxic drugs can cause bone marrow failure. As these drugs kill rapidly
dividing cells, the development of decreased production of white blood
cells can arise and open the pet up to life threatening
When to Decrease
every 3-6 weeks, medications should be decreased by 25-50%. Factors that are important in
deciding treatment adjustments include trends in the hematocrit and
resolution of clinical signs in the dog compared to prior
examination. Cocker spaniels
tend to be weaned a little slower, and large pets may tend to be weaned
over longer time periods because of the higher level of medications they
were on. Most pets should be
off medications by one year and then be checked 3-4 times per year for the
first year, and then yearly after that.
AIHA/IMHA is a
life threatening immune disease that can cause damage to vital organs
through the lack of oxygen supply associated with the resultant
anemia. Owners of pets with
AIHA/IMHA face a guarded to poor prognosis for the pet at the time of
diagnosis. If an underlying
disease such as cancer is discovered--the prognosis becomes complicated by
the limitations associated with the underlying cause as well.
the destruction of RBC can result in development of blood clotting
disorders and a systemic inflammation syndrome that looks like a severe
infection clinically—the aftereffects of these can also cause organ damage
to kidneys, lungs and other organs resulting in death or prolonged
This brochure was written with the wonderful help and support from Dr. Robert Murtaugh of Dove Lewis Emergency Animal Hospital and Dr. Elizabeth Rozanski from Tufts University School of Veterinary Medicine. The material in this brochure was written to use as an aide for others to learn about this terrible disease and its effect on their pet. Thank you.
Dr. Robert J. Murtaugh, DACVIM, DACVECC is a graduate of the University of Minnesota, College of Veterinary Medicine. Dr. Murtaugh was formerly on the faculty at Tufts University School of Veterinary Medicine and is currently the Director of Critical Care at the Dove Lewis Emergency Animal Hospital in Portland, Oregon. Dr. Murtaugh chaired the organizing committee to establish the American College of Veterinary Emergency and Critical Care (ACVECC). He is a past-president (1994-1996) of the Veterinary Emergency and Critical Care Society and currently President-elect of ACVECC.
Rozanski, DACVIM, DACVECC is a graduate of the University of
Illinois. She completed a
residency in Emergency and Critical Care medicine at the University of
Pennsylvania and is currently an Assistant Professor at Tufts University
School of Veterinary Medicine.
Immune-Mediated Hemolytic Anemia and Immune-Mediated Thrombocytopenia, Textbook of Veterinary Internal Medicine—Client Information Series, Carol Norris, DVM, DACVIM. Copyright 2000 by W.B. Saunders Company
Beau's Story : http://home.comcast.net/~joan.ogg/beau.htm
Support from others with experience:
This information is also available as a printed brochure. If you would like a copy of this brochure please click on the link below to go to the AIHA file document page.
Published and updated on: 04/26/2006 09:29 AM