200 Commerce Street | Williston, VT 05495
Joey’s owners were worried. After having been sprayed by a skunk directly in the face a few days before, this 4 year old Chihuahua mix had never returned to his happy old self. His skin looked yellow, his gums were very pale, and he was passing dark orange urine. They brought him to the Burlington Emergency and Veterinary Specialists Hospital where it was quickly discovered that, for some unknown reason, his body was destroying his red blood cells and he would need to be admitted to the hospital for emergency supportive care. Joey had a disease called autoimmune hemolytic anemia and he was in need of blood transfusions and medications to stop the immune system’s attack.
Normally, red blood cells are produced in the bone marrow and then released into the circulation. As the red blood cells age or become damaged, they will be removed from the circulation and will be recycled to form new red blood cells. The number of red blood cells may become reduced if there is a decrease in the bone marrow’s production of or increased loss of them from the circulation.
Anemia is a medical term referring to a reduced number of circulating red blood cells and is not a specific disease but rather is a symptom of an underlying disease process or condition. Red blood cells deliver oxygen to the body’s tissues, therefore a patient who is anemic will suffer from symptoms related to a lack of oxygen such as weakness or rapid, shallow breathing.
Autoimmune hemolytic anemia (AIHA) is an immune system disease in which the body attacks and destroys its own red blood cells. In dogs with AIHA, red blood cells are still being manufactured in the bone marrow, but once released into the circulation, they have a shorter-than-normal life span. AIHA may be primary or idiopathic (an unknown underlying cause), or it may be secondary to another disease process.
With primary AIHA, the dog’s immune system is not working properly and it makes antibodies that target its own red blood cells. With secondary AIHA, the surface of the red blood cells becomes altered by an underlying disease process or a toxin. The dog’s immune system then recognizes these red blood cells as ‘foreign’ invaders that must be destroyed. Secondary AIHA may be triggered by cancer, infections (especially tick borne diseases), blood parasites, drug reactions, snake bites, chemicals, toxins, bee stings, and, perhaps as in Joey’s case, skunk spray.
Most dogs with AIHA have severe anemia, and their gums will be very pale rather than the normal pink to red color. Dogs with anemia will be listless and will tire more easily because there are not enough red blood cells to carry oxygen to the tissues. To compensate for this lack of oxygen to the tissues, the heart rate will increase and the patient will breathe more rapidly.
As the disease progresses, excessive levels of bilirubin, a breakdown product of ruptured red blood cells, build up within the body. Some of this excess bilirubin spills over into the urine, causing it to appear dark. This excessive level of bilirubin can also cause the skin, gums and other mucous membranes to appear yellow, or icteric.
Anemia is diagnosed by performing a blood test called a Complete Blood Count (CBC). The CBC measures a number of different values in a sample of whole blood. To test for anemia, the number of red blood cells are counted and the individual cells are examined under a microscope to determine their size and shape. With AIHA, the number of red blood cells will be low and the size and their shape abnormal. In many cases of AIHA, there will also be evidence of ‘autoagglutination’ or abnormal clumping of red blood cells.
Because Joey’s anemia was so severe he needed a blood transfusion. When anemia becomes life-threatening, a blood transfusion is administered to stabilize the dog while the underlying cause of the anemia is determined and other treatments can begin to take effect. Before giving a transfusion, blood samples will be taken for diagnostic testing.
If the AIHA is secondary, the treatment will be directed at the underlying cause, such as the infection or toxin. If no underlying cause can be detected, as is most often the case, or if the disease is determined to be primary or idiopathic, immunosuppressive therapy will be used. Immunosuppressive medications are drugs that inhibit or prevent the activity of the immune system. In some cases of idiopathic AIHA, the dog will respond rapidly to treatment with immunosuppressive doses of corticosteroids. In other cases, the patient may require a combination of immunosuppressive medications to get the condition under control.
Joey responded very well to his life-saving blood transfusion and medications. He was discharged from the hospital a few days later and is recovering well at home today. He comes in for monthly recheck blood work as his medications are slowly tapered down and the owners happily report that he is the old Joey once again.
-Tanya Donovan, DVM, Diplomate ACVIM