Immune Mediated Hemolytic anemia in dogs - causes and treatment
The function of the immune system in a dog’s body is to recognize and destroy foreign substances and pathogens. Sometimes this system can go awry due to one reason or the other and starts attacking the body’s own cells. Conditions caused by such self-destructive responses are known as autoimmune or immune mediated diseases.
The immune system normally removes and destroys red blood cells that are four months old. New red blood cells are produced in the bone marrow to replenish the loss. Immune mediated hemolytic anemia is a condition where the immune system starts destroying red blood cells more than the bone marrow can produce. It is not difficult to explain how this comes about to happen. Certain foreign substances like toxins, parasites and drugs, which the immune system must destroy sometimes cling to red blood cells. In its attack on the foreign agents it happens to harm the red blood cells also.
Red blood cells marked for destruction and coated with antibodies circulate through liver, spleen and bone marrow. The iron in them is sent to the liver for recycling. The liver finds that it has to process more iron than it can handle. This causes jaundice, a typical symptom of liver disease in dogs . Red blood cells carry oxygen from the lungs to the different parts of the body. Inadequacy of red blood cells (anemia) causes ‘oxygen starvation’ leading to some symptoms that are similar to liver disease in dogs such as lethargy, loss of appetite along with other symptoms of unwillingness to exercise depression and panting.
Immune mediated hemolytic anemia can be classified as primary or secondary. Laboratory tests do not reveal any fundamental cause behind a primary condition. Secondary disease, however, is caused when the immune system unknowingly destroys its own blood cells while fighting an underlying condition. This could be a disease like cancer or an infection or exposure to a toxin or drug.
Platelets (thrombocytes) are tiny bits of protoplasm in blood, which are responsible for blood clotting. Immune Mediated Thrombocytopenia is a disease in which the immune system starts destroying platelets. This leads to excessive bleeding from the gums, skin or nose and occasionally through feces or urine. Excessive loss of blood may also cause severe anemia. At times both immune mediated hemolytic anemia and thrombocytopenia may occur together.
Treatment involves suppression of the immune system so that the red blood cells or platelets (in case of thrombocytopenia) are spared from involuntary attacks. The most frequently used drug is prednisone, a steroid hormone that works as an immunosuppressant. The drug is continued along with constant monitoring till the tests reveal a significant improvement in complete blood count.
Long term use and higher doses of steroids have accompanying side effects that include increase in thirst and urination, predisposition to urinary tract infections, re-distribution of body fats and symptoms associated with Cushing’s syndrome. If the response is missing or too slow, stronger immunosuppressive agents are used, which are serious drugs and have a different set of more serious side effects.
Like feline liver disease, immune mediated hemolytic anemia too is more prevalent in dogs than cats but its prevalence can be equally devastating in both cases. If an underlying condition is discovered, it is vital that an attempt be made to correct that problem concurrently with treating the immune disease.
