Immune mediated hemolytic anemia (IMHA), which is also called autoimmune hemolytic anemia (AIHA), is a disease that is caused by an immune system gone awry. In some cases, the disorder may be initiated by infections, cancer, medications or vaccination, but in many others, no underlying trigger can be indentified. Whatever the cause, the body's immune system inappropriately identifies its own red cells as a potential threat and attacks and destroys them. Immune mediated hemolytic anemia most commonly affects middle-aged, female dogs. Some breeds (e.g., cocker spaniels) are genetically predisposed.
Affected animals generally have pale or yellow skin and mucous membranes, are very weak, and breathe more deeply and rapidly than is normal. A veterinarian may also detect a very large spleen when palpating the abdomen. The results of blood work, urinalysis and a Coombs' test can help differentiate IMHA from other disorders that have similar symptoms, like liver disease or parasitic infections of red blood cells.
Treatment for immune mediated hemolytic anemia includes fluid therapy, medications that suppress the body's immune system, and dealing with any identifiable underlying disorders. Severe cases may also require blood transfusions and supplemental oxygen. An animal's prognosis depends on the severity of a bout of IMHA and how rapidly and aggressively it is treated. Dogs that survive the initial crisis can sometimes be tapered off their immunosuppressive drugs over a period of a few months while they are closely monitored for a relapse.
Written by: Jennifer Coates, DVM
Last reviewed: October 2, 2008