Anemia in Dogs (cont.)

Immune-Mediated Hemolytic Anemia

This is the most common cause of hemolysis in adult dogs. Red blood cell destruction is caused by auto-antibodies that attack antigens present on the surface of the cells, or by antigens from medications or organisms attached to the red blood cell walls. The weakened cells are trapped in the spleen and destroyed.

Poodles, Old English Sheepdogs, Irish Setters, and Cocker Spaniels are predisposed to immune-mediated hemolytic anemia, but all breeds are susceptible. Affected dogs are usually between 2 and 8 years of age; females outnumber males four to one.

Most cases of immune-mediated hemolytic anemia are idiopathic. That is, the reason why the auto-antibodies developed in that particular dog is unknown. In some cases there is a history of recent drug therapy. An immune-mediated hemolytic anemia also occurs with systemic lupus erythematosus.

The diagnosis is made by microscopic examination of blood smears, looking for specific changes in the appearance of the erythrocytes and other blood elements; and by serologic blood tests.

Treatment: Treatment of idiopathic immune-mediated hemolytic anemia is directed toward preventing further red cell destruction by blocking the antigen-antibody reaction using corticosteroids and immunosuppressants. Severe anemia is corrected with blood transfusions. Splenectomy (removal of the spleen) may be beneficial, but only when tests prove that the spleen is contributing to the hemolytic process.

The response to treatment depends on the rate of hemolysis and whether an underlying cause can be found and corrected. The outlook is guarded; even with appropriate medical treatment, the mortality rate is close to 40 percent.