Immune-Mediated Hemolytic AnemiaLiaison: Patti Emmett, MS, RN, CIC
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Signs and Symptoms
weakness and/or loss of energy
decreased interest in food
jaundice (yellow tinge in the whites of the eyes)
a slight fever may be present.
In many cases (60-70%), a cause isn't found. In some cases, a primary reaction by the immune system precedes the act of red blood cell destruction.
The immune system (lymphocytes) begins to attack the body's own RBCs with destructive antibodies. RBCs normally carry oxygen to tissues, and carry away waste. Iron and bilirubin are sent to the liver in larger amounts than normal causing jaundice and impaired liver function.
Altered liver function, lack of adequate tissue oxygen, and complications of blood clot formation can be life-threatening.
Cancer (e.g. hemangiosarcoma) and drugs can trigger the immune system to overreact. (The immune system starts targeting proteins that resemble the drug; RBCs are destroyed as "innocent bystanders"). Examples of implicated drugs include trimethoprim-sulfa and methimazole.
Blood cell counts can determine if the numbers of red blood cells are normal or too low (anemia). Anemia can occur from bleeding or from increased RBC destruction (IMHA).
The bone marrow tries to make more RBCs to replace the destroyed, mature RBCs. Because the bone marrow can't keep up with the destruction, immature forms of RBCs ("reticulocytes" and "nucleated RBCs") may be released into the blood.
Additional testing can determine if the bone marrow is not responding. This may be temporary and resolve, or persist.
Note: Treatment of animals should only be performed by a licensed veterinarian. Veterinarians should consult the current literature and current pharmacological formularies before initiating any treatment protocol.
Prednisone and dexamethasone for immunosuppression.
Azathioprine if no response to above.
Transfusion when a crisis occurs.
Barlough,J.E., Pedersen, N.C, 1995. "The immune system and disorders" in UC Davis School of Vet Med book of dogs. Siegal, M. Ed., p.331-333. Harper Collins, New York.
Hemolytic Anemia in the Merck Veterinary Manual.
Kohn, B., 2003. Evans’ syndrome: immune-mediated hemolytic anemia in Immune-mediated thrombocytopenia-current approach. 28th World Congress of World Small Animal Veterianry Assoc., Thailand. P. 1-3.
Trepanier, L.A., Danhof, R., Toll, J., and Watrous, D. 2003. Clinical findings in 40 dogs with hypersensitivity associated with administration of potentiated sulfonamides. J Vet Int Med 9; 17(5):p. 647-652. Link to abstract
Holloway, S.A., Meyer, D.J, and Mannella, C. 1990. Prednisolone and danazol for treatment of immune-mediated anemia, thrombocytopenia, and ineffective erythroid regeneration in a dog. J Am Vet Med Assoc 197 (8):1045-1048. Link to abstract