Anemia is defined as a low red blood cell count. The red blood cells’ primary function is to transport oxygen to tissues. If tissues do not get enough oxygen, it can be deadly. Immune-mediated hemolytic anemia occurs when the body’s immune system destroys its own red blood cells. Certain breeds of dogs are predisposed to this kind of anemia. They include cocker spaniels, poodles, West Highland white terriers, old English sheepdogs, schnauzers and Irish setters.
Immune-mediated hemolytic anemia can be either primary or secondary. In the primary form, the immune system incorrectly recognizes the blood cells as foreign and destroys them. The secondary form is caused by toxins, infections, blood parasites, cancer, drug reactions or inherited red blood cell defects. In dogs, 60 to 75 percent of immune-mediated hemolytic anemia cases are primary and not related to an underlying cause. In cats, the secondary form is more common and is associated with feline leukemia virus or blood parasites.
Clinical signs typically include weakness, lethargy, increased heart rate, poor appetite and pale gums. Other signs may be fever, jaundice (yellowing of skin), eating abnormal objects (pica), vomiting, diarrhea, weight loss or depressions. Death can occur rapidly if the red blood cells’ destruction is severe.
Treatment options include hospitalization with potentially multiple blood transfusions. Oxygen therapy, intravenous fluid therapy and intense monitoring of the red blood cells may be recommended to stabilize the patient. Treatment is then directed at the underlying cause and may include immune-suppressive drugs, antibiotics, parasite control, chemotherapy or other measures.
For primary immune-mediated hemolytic anemia, the main treatment involves multiple medications to suppress the immune system. Responsive cases may be hospitalized for seven to 14 days, and longer hospital stays are often needed for severe cases.
For patients that respond quickly to medications and do not need repeated blood transfusions, the prognosis is good. However, immune-mediated hemolytic anemia can be an extremely dangerous disease, especially in patients with yellow skin (jaundice) and blood clots. Mortality rates of 20 to 80 percent have been reported. Just because a dog has recovered from anemia does not mean that it is healthy for life. Around 15 percent of dogs will get the condition again. Relapse is minimized in dogs with long-term use of steroids and azathioprine.
Dr. Allani Delis is a veterinarian at St. Francis Pet Clinic.