Immune Mediated Hemolytic Anemia in Cats (IMHA), Autoimmune Hemolytic Anemia


Overview of Immune Mediated Hemolytic Anemia in Cats (IMHA)

Immune mediated hemolytic anemia (IMHA), also known as auto-immune mediated hemolytic anemia (AIHA), is a disease in which the body’s immune system, which is designed to attack and kill germs, attacks and kills the body’s own red blood cells. The attack begins when antibodies, which are molecules made by the immune system to target germs, instead attach to and target the animal’s own red blood cells for destruction. The red blood cells carry oxygen to the tissues, and the animal cannot survive without adequate oxygenation of the tissues.

Below is an overview about Immune mediated hemolytic anemia (IMHA) in cats followed by detailed information about the diagnosis, treatment and prognosis of this serious condition. 

The causes of IMHA remain largely unknown. While some cases of IMHA may be associated with a triggering event (cancer, infection, and perhaps even vaccinations), these events do not explain why the immune system misdirects its arsenal of weapons against the animal it is meant to protect.

IMHA occurs more often in dogs than in cats. It is most commonly reported in young cats and there is known breed predisposition in cats.

IMHA is a rapidly life-threatening disease. Even with appropriate treatment, this disease can be fatal.

What To Watch For

  • Pale gums
  • Yellow tinged gums or whites of the eyes
  • Dark or dark yellow urine
  • Tiring easily, weakness
  • Lethargy
  • Loss of appetite
  • Vomiting
  • Tachypnea (rapid breathing)
  • Diagnosis of IMHA in Cats 

    Your veterinarian will recommend the following tests:

  • A complete history and medical examination. Be prepared for questions about any medications your animal may have received, when the most recent vaccinations were given, and questions about the color of urine and stool.
  • Complete blood count (CBC) should be performed on all cats suspected of having anemia (decreased number of red blood cells), regardless of the cause.
  • A “packed cell volume,” or PCV, is a quick and simple test for the number of red blood cells present.
  • Reticulocyte counts allow the veterinarian to determine if new red cells are being made in appropriate quantities.
  • A serum biochemical profile and urinalysis may be performed to give clues as to possible causes of the anemia.
  • A saline agglutination test is a simple blood test that may show if the red cells are clumping together.
  • Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) testing may be recommended to look for an underlying cause of IMHA.
  • A Coombs test is often indicated. A sample of your pet’s blood is incubated with special reagents to look for evidence of an immune reaction to the blood.
  • Radiographs, ultrasound examinations, or blood tests for infectious diseases may be indicated in some patients. These examinations may help rule out causes of anemia other than IMHA, or may help identify triggers that preceded development of IMHA.
  • Treatment of IMHA in Cats

  • Corticosteroids (such as prednisone, prednisolone, or dexamethasone) are the mainstays of treatment for IMHA. They suppress the immune system’s attack on the red cells.
  • In the most severe cases, or those cases that fail to respond to corticosteroids, other immunosuppressive agents may be utilized. These include drugs such as azathioprine, cyclophosphamide, cyclosporine, danazol, or leflunomide.
  • Intravenous immunoglobulins, a product made from human blood, has been used with some success in a few cases of IMHA.
  • Plasmapheresis, or the process of removing antibodies from the blood, is very rarely available to veterinarians, but may be possible in some special hospitals.
  • Because the spleen is responsible for removing many of the antibody targeted red cells, splenectomy (removal of the spleen) may benefit some animals after initial treatment and stabilization.
  • Supportive care is essential to the successful treatment of IMHA. Such care may include transfusion, nursing, and medications.
  • Transfusion of either whole blood (cells plus the liquid plasma) or of packed red blood cells (cells only after the liquid is removed) may prove life saving.
  • Administration of a blood substitute (Oxyglobin®) provides the ability to carry oxygen to the tissues without administering blood itself.
  • Complications of IMHA include the formation of blood clots. Heparin is a medication that helps prevent formation of these clots.
  • Intravenous fluids may be indicated to prevent dehydration in some pets.
  • Home Care and Prevention

    It is crucial to administer all prescribed medications as directed. Even a few missed doses can have serious consequences.

  • Allow the pet to limit his activity. Anemic animals should not be encouraged or expected to engage in active play.
  • Provide adequate nutrition. Encourage the pet to eat a well-balanced pet food, but your veterinarian can suggest appropriate enticing treats for the animal that refuses food.

    Because we do not understand what causes IMHA, there are no known preventive measures.                                

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