Hemolysis is an acceleration in the normal process of red blood cell breakdown. Red blood cells break down to form bile and hemoglobin. With severe hemolysis, these breakdown products accumulate in the body.
The dog appears weak and pale, and has a rapid pulse. The spleen, liver, and lymph nodes may be enlarged.
Causes of hemolysis include immune-mediated hemolytic anemia, congenital hemolytic anemia, infectious diseases (such as canine babeiosis and leptospirosis), drug reactions to medications such as acetaminophen, and poisonous snake bites. A number of bacteria produce toxins that destroy red blood cells, so hemolysis can also occur with severe infections.
Immune-Mediated Hemolytic Anemia 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 to it. Affected dogs are usually between 2 and 8 years old with females outnumbering males 4 - 1.
Most cases of immune-mediated hemolytic anemia are idiopathic - the reason for the development of the antibodies development 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.
Congenital Hemolytic Anemia
Several inherited abnormalities in the structure of red blood cells can result in their premature destruction. Phosphofructokinase deficiency is an autosomal recessive trait that occurs in English Springer and Cocker Spaniels. A deficiency of this enzyme results in changes in the pH of red blood cells, causing the cells to periodically fragment and produce bouts of hemoglobinuria.
Pyruvate kinase deficiency is another red blood cell enzyme deficiency caused by an autosomal recessive gene. This disease is recognized in several breeds including Basenjis, Beagles, and West Highland Terriers. Puppies usually develop the hemolytic anemia at 2 - 12 months of age. Death by age 3 is the usual outcome.
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 also by serologic blood tests.
Immune-Mediated Hemolytic Anemia
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 (the 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%.
Congenital Hemolytic Anemia has no effective treatment.
Genetic tests for Phosphofructokinase and pyruvate kinase deficiency are available through the University of Pennsylvania at PennGen, and from OptiGen and VetGen.
OFA maintains a voluntary diagnostic service and registry for dogs with Phosphofructokinase deficiency, and Basenjis with pyruvate kinase deficiency in cooperation with the respective US national breed clubs.
Please contact your veterinarian if you think your pet may have this condition.
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