Red blood cells (RBCs) contain the protein hemoglobin, which carries oxygen to all cells and tissues of the body.  In hemolytic anemia in dogs, the RBCs are destroyed, which deprives the body of the oxygen it needs to function.  Hemolytic anemia in dogs can be caused by a variety of problems, including infection with viruses or blood parasites (eg, Babesia), toxins, poisonous plants, drug reactions, and conditions such as diabetes or liver disease.  However, the most common cause in dogs is autoimmune hemolytic anemia, in which antibodies of the dog’s own immune system attack the circulating RBCs.

In autoimmune hemolytic anemia, foreign proteins coat the RBCs.  The immune system then sees these cells as invaders, and so attacks and destroys them.  Autoimmune hemolytic anemia can be triggered by cancer, an infection, or a drug or vaccine reaction.  However, the exact cause usually remains a mystery.  The condition is most common in young to middle-aged dogs, especially in poodles, cocker spaniels, and old English sheepdogs.

As with anemia from any cause, common signs include pale mucous membranes and lack of energy.  The breakdown of hemoglobin from the RBCs can cause jaundice, so that the eyes, gums, and even skin can take on a yellowish tint.

Diagnosis begins with a physical examination and routine blood tests to exclude bleeding or other causes of anemia, such as depression of the bone marrow.  X-rays may be recommended to look for cancer or signs of lost bone marrow.  The definitive diagnostic test for autoimmune hemolytic anemia is a Coombs’ test, which is a blood test that looks specifically for antibodies attached to RBCs.

Treatment is aimed at correcting the underlying cause and restoring RBC numbers.  In autoimmune hemolytic anemia, high levels of corticosteroids (or more potent medications) are used to suppress the immune system and stop the RBCs from being destroyed.  Dogs often need to be hospitalized for treatment (with fluids and possibly blood transfusions) and monitoring.  The overall prognosis is good for dogs that respond quickly to treatment, but about one-third of dogs with autoimmune hemolytic anemia do not survive.

Q&A

What is hemolytic anemia?

Hemolytic anemia is a condition in the red blood cells are destroyed, leading to anemia.

What causes hemolytic anemia?

This disorder can have a variety of causes, including blood infections, poisoning, and metabolic diseases such as diabetes.  However, the most common cause in dogs is an autoimmune condition in which antibodies from the dog’s own immune system attack the circulating red blood cells.

How is autoimmune hemolytic anemia diagnosed?

Routine blood tests can provide important diagnostic information, but definitive diagnosis requires a Coombs’ test, which is a specialized blood test that looks for antibodies on the red blood cells.

How is autoimmune hemolytic anemia treated?

High levels of corticosteroids are used to depress the immune system and reduce the destruction of red blood cells.  If this treatment is unsuccessful, more potent immunosuppressive medications can be tried.