autoimmune part 2: Immune-mediated hemolytic anemia
A middle-aged Cocker Spaniel is brought into the veterinary clinic with a complaint of two days of lethargy, decreased appetite and weakness. A physical exam reveals pale mucous membranes with the pronounced yellowing of jaundice, a rapid heart rate and an enlarged spleen. This patient is a classic picture of immune-mediated hemolytic anemia (IMHA).
What is immune-mediated hemolytic anemia?
IMHA, an autoimmune disease, occurs when the body’s immune system suddenly begins to identify red blood cells – those responsible for transporting oxygen throughout the body – as foreign invaders. The intense attack launched against these red cells causes them to burst open within the blood vessels and to be taken out of circulation by the spleen.
The rupture of these cells spills pigment into circulation, which leads to the yellowing of the skin and mucous membranes. The red blood cell count drops precipitously, leading to a rapidly progressive, life-threatening anemia. This anemia causes profound weakness and lethargy.
Immune-mediated hemolytic anemia can occur in cats and dogs, but is more common in dogs. For the majority of cases, there is no known inciting cause, but there are some breeds that are predisposed, with Cocker Spaniels being one of the most affected. Less commonly, IMHA can be linked back to infections, tumors, toxins or certain parasites such as heartworms. Whether or not there is an identifiable underlying cause, the progression of the disease is similar, with ongoing red blood cell destruction and resulting anemia.
How is it diagnosed?
Diagnosing this condition involves identifying the anemia and then the verification that it is an autoimmune process. This verification includes test called the Coombs test, evaluation of the red blood cells under a microscope and a test called a saline agglutination test. These tests are often used in combination to verify a diagnosis of IMHA.
Treatment of immune-mediated hemolytic anemia involves intensive supportive care for the anemia through the use of blood transfusions and fluid therapy, supportive care for any secondary problems that can arise and aggressive suppression of the immune system to stop the ongoing red blood cells destruction. If any underlying cause is suspected, it must be treated as well.
Unfortunately, the prognosis for even an aggressively treated IMHA is very guarded, and the cost of treatment can be thousands of dollars – it’s definitely one situation where protecting your pet with dog insurance or cat insurance can come in handy. That being said, I have seen a number of pets recover from IMHA and go on to lead long, healthy lives.