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a primer on immune mediated hemolytic anemia (imha)

  • Dr. Kim
  • Posted by Dr. Kim Smyth on
    Staff Veterinarian and Pet Health Writer of Petplan

Immune mediated hemolytic anemia (or IMHA, for short) is a life threatening blood disorder.  To understand this long-named disease, let’s break it down into parts:


Immune mediated = the immune system malfunctions, and begins destroying cells in the body

Hemolytic = breakdown of red blood cells

Anemia = low levels of hemoglobin and red blood cells


Put them all together, and you’ve got a condition in which an overactive immune system targets too many red blood cells for destruction, resulting in moderate to severe anemia.


Red blood cells serve a vital function, delivering oxygen from the lungs to all of the tissues of the body. They have a natural life span of about two months in cats and three months in dogs. In a normal animal, red blood cells are removed as they circulate through the spleen, liver and bone marrow about as fast as they are made, so the total number of red blood cells stays level.


When an animal has IMHA, the body’s immune system marks too many red blood cells for removal. Over time, so many red blood cells are destroyed that there aren’t enough in circulation to perform their job delivering oxygen to vital tissues.


IMHA may have an underlying cause, or it may not. In 60 percent to 75 percent of IMHA cases in dogs, an underlying cause is never found. In cats, IMHA is generally caused by feline leukemia or by a blood parasite called Mycoplasma hemofelis.


Symptoms of IMHA are due to the anemia. You’ll notice your pet becoming lethargic and weak, and the gums and lips may become pale. You may also notice jaundice, or a yellowing of the gums and whites of the eyes. Urine may contain the breakdown products from the red blood cells, so it may be orange or brown in color.


Your veterinarian will use a blood test to diagnose IMHA, and she will likely want to perform other tests as well. By looking at your pet’s blood sample microscopically, she may be able to find other clues, like misshapen red blood cells, cells that clump together, or the presence of immature red blood cells. Finally, she may send off a Coomb’s test, which looks for antibodies on the red blood cells.


Treatment of IMHA centers on suppressing the body’s inappropriate immune response. If the immune system can be quieted, red blood cells will stop being targeted for destruction. High-dose steroids are used to suppress the immune system. If ineffective, other more potent immunomodulators will be considered. In the meantime, other supportive treatment, like IV fluids and nutritional support, will be provided. Many patients with IMHA will find their anemia severe enough to require blood transfusions.  If you haven’t already guessed, IMHA is serious and often requires lengthy hospitalization. Having dog insurance or cat insurance with Petplan pet insurance can provide you with peace of mind that your pet's stay in the hospital, as well as any necessary treatments, can be covered. 


Once your pet is feeling better, you’ll be sent home with orders to continue your pet’s steroids, which you’ll slowly taper off over weeks or months. During this time, you will likely have several rechecks to make sure your pet is on the right path. It’s important to be vigilant during this rocky time – be sure to report any setbacks your pet may have while her medication is being tapered.  

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Posted by Rachel Schreiner
on November 05 2014 15:06

My 4yo female Australian Kelpie/Pit bull mix, Sydney, was normally on Advantage flea medication. My father offered me a tube of Frontline because his dog was currently receiving chemotherapy for lymphoma and he was told by the vet to discontinue the topical flea medication during chemotherapy. Shortly after administering Frontline, she seemed depressed and became increasingly lethargic. Three months later (and 2 doses later) she became so listless (it almost seemed overnight because the lethargy was so gradual) that my husband and I rushed her to the vet. Initially, the vet suspected rat poisoning due to low red blood cell count. Sydney's rbc was at 12%. Normal range is 39-60%. After a Coomb's test was performed (a special blood test to check for certain antibodies, she was diagnosed with immune mediated hemolytic anemia or IMHA. Her immune system was attacking her red blood cells. It's been a month since her diagnosis and she will still require further treatment. We have spent $1500 in just 4 weeks. She will need blood tests at least every 2-3 weeks for several months along with vet rechecks and medication. I wish we would have purchased pet insurance, as there are no companies that offer insurance for pre-existing conditions or any complications, further exams, or anything related to this disease. We are considering purchasing pet insurance for anything else.

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