Autoimmune Hemolytic Anemia (AIHA) is a disease in which the body’s immune system recognizes it’s own red blood cells as foreign, attacks and destroys them. This is usually initiated by an exposure to bacteria or a virus. The body’s immune system responds appropriately to fight the invading organism by producing antibodies against it, but malfunctions and also produces antibodies against red blood cells.

Red Blood cells carry oxygen to all cells of the body, and are produced in bone marrow. In AIHA, the bone marrow continues to produce red blood cells, but hemolysis (heme=blood; lyse=destroy) outruns the production of new cells and the animal becomes anemic. This can occur either acutely (quickly) or chronically (over time).

As the red blood cells are destroyed, hemoglobin (the molecule in the red blood cell that carries oxygen) can build up to high levels. The liver tries to break it down and dispose of it. Elevated levels of bilirubin (the breakdown products) cause a yellowish tint to the skin, mucous membranes and sclera of the eyes (jaundice). These breakdown products may also be excreted in the urine, making it appear tea-colored. Jaundice is usually quite apparent when AIHA is acute.

AIHA is reported to be very rare in felines, and is not thought to be of a genetic nature, however it’s appearance in our foundation lines is demonstrating a recessive tendency. Please refer to the tables following this text.

Symptoms

The signs of AIHA include weakness, lethargy, poor appetite and weight loss. Mucous membranes and nose leather (if pink) become pale. Heart rate and respiratory rate increase to compensate for the lack of sufficient circulating oxygen. Skin, mucous membranes and sclera (the white of the eye) may become tinted with yellow (jaundice). Some bruising may be apparent.

  Underlying causes for anemia should be ruled out and treated appropriately such as FeLV, FIV, FIP, and hemobartonellosis (blood parasite transmitted by fleas and mosquitoes). Exposure to onion, Tylenol and glycol should be assessed.

Diagnosis

CBC

Assess for anemia and presence of developing red blood cells

Assess for potential for clotting problems

Assess for potential infection

Chemistry screen

Assess for evidence of red blood cell destruction and/or other reasons for anemia

Coombs test (positive)

Bone Marrow aspiration

Assess red blood cell development

Clotting times

Assess potential for blood clotting abnormality

Urinalysis

Assess for hematuria (blood in the urine)

Assess for hemoglobinuria

Radiographs

To evaluate the spleen and liver (may be enlarged)

Treatment

Any underlying disease should be treated appropriately. In the case of hemobartonellosis, the cat should be treated with a tetracycline-type antibiotic.

Treatment includes steroid therapy (prednisone, dexamethasone) and more potent immunosuppressive drugs. Blood transfusion with cross-matched blood can be used in acute situations, but may set up a more powerful immune response. Erythropoietin may be used to stimulate the increased production of red blood cells by the bone marrow, but takes up to 3 weeks to be effective.

If medical management fails to control the autoimmune response after four to six weeks, surgical removal of the spleen may be helpful.

Prognosis

The prognosis for this disease is guarded. If the cat is stabilized and maintained with medical management, there are risks associated with the treatment, such as increased potential for infection, gastric ulcer, Cushing’s syndrome and steroid-induced diabetes. There is also the risk for relapse. Continual evaluation of the cat is necessary (including regular CBC) to catch symptoms of a relapse in the early stages in order to resume treatment. Lifelong therapy may be necessary.

Click to subscribe to aha-nfc