Immune-Mediated Hemolytic Anemia, Canine - contd.
Hemolytic anemia may occur secondary to an underlying trigger or cause. Such causes can include red blood cell parasites, tick-borne infectious diseases, exposure to vaccines or other biologic products, medications, bee stings, toxins like zinc or onions, and cancer. In some specific breeds, inherited red blood cell enzyme abnormalities can trigger hemolytic anemia. Although the underlying cause of anemia in these instances is hemolysis, or red blood cell breakdown, not all of these cases are due to hemolysis that is immune system-related.
There are many possible triggers for the development of immune-mediated hemolytic anemia. Sometimes IMHA is associated with exposure to certain medications that may alter the red blood cell membranes, or that serve as a stimulus for antibody production themselves. Red blood cell parasites may either attach to the red blood cell membranes or invade the red blood cells directly, triggering an immune response. Infectious diseases like ehrlichiosis may be associated with immune-mediated hemolysis. Some forms of cancer, particularly lymphosarcoma, can serve as triggers for IMHA. However, in most patients, there is no identifiable trigger or obvious underlying, associated condition. This situation is referred to as idiopathic immune-mediated hemolytic anemia. The exact cause of this syndrome and the mechanisms that perpetuate it are not completely understood. In these patients, some abnormality in the immune system allows for the destruction of otherwise normal red blood cells. Veterinarians believe that there may be a hereditary predisposition to this condition. It may occur alone or in conjunction with other immune-mediated disorders.
