Immune mediated hemolytic anemia (IMHA) is a life-threatening disease in dogs. This disease is also called autoimmune mediated hemolytic anemia because the dog’s immune system actually makes antibodies against it’s own red blood cells. If large numbers of antibodies attach to a red blood cell, it will lyse or burst open inside the bloodstream. Red blood cells with only a few antibodies on their surface will be destroyed by the spleen or liver. Either way, red blood cells are destroyed causing anemia.
Dogs with IMHA usually come into the clinic breathing fast and hard. It is more common in females than males. Their gums are often pale with a hint of yellow (jaundice) due to the release of hemoglobin normally found inside the red blood cells. To diagnose this condition, a drop of blood is mixed with a drop of saline. The antibodies on the surface of the red blood cells make them stick together and clumping will be observed. To me, it looks like pepper.
Once the diagnosis of IMHA is made, I try hard to classify it as either primary or secondary. Secondary means the immune response was caused by something like infection, drugs, parasites, poisons, insect stings, cancer or vaccination with a modified live vaccine. In Arizona, I see a lot of IMHA caused by tick fever (Erhlichia). Primary means that no inciting factor is found. In my experience, these cases are associated with a poorer prognosis.
The goal of treatment is to stop the destruction of the red blood cells with immunosuppressive therapy. If the patient’s anemia is severe, a blood transfusion may be required. Transfusions are only given in critical situations because the new red blood cells will stimulate the patient’s immune system even if they are cross matched. In secondary IHMA, the inciting cause is treated when possible. In dogs who do not respond well to drug therapy, surgical removal of the spleen will often help.
Females are more prone to this disease than males. According to the literature, the following breeds are predisposed: cocker spaniel, collie, English springer spaniel, French poodle, Irish setter, miniature schnauzer and old English sheepdog. In my experience, I see it in these breeds plus Yorkshire terriers and Pomeranians.
-Vasilopulos, R. & Mackin, A. Immune Mediated Hemolytic Anemia (IMHA). VIN Associate Database, updated 11/10/2005.