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Putnam North Animal Hospital
Immune Mediated Hemolytic Anemia
The Basics
Anemia is a condition where there is a lower than normal number of red blood cells in the bloodstream. Red blood cells are important because they supply oxygen to all parts of the body, and when severe anemia is present, all of the body’s tissues are oxygen-deprived, leading to symptoms such as sluggishness, loss of appetite, and even collapse and unconsciousness.

Immune-mediated hemolytic anemia (IHA) is a particular type of anemia in which the number of red blood cells is low because they are destroyed (hemolyzed) by the body’s own immune system. In the healthy body, the immune system attacks foreign invaders such as bacteria and viruses. However, in immune-mediated hemolytic anemia, the body misidentifies normal healthy red blood cells as foreign and destroys them faster than the body can replace them. In some pets, the onset of this disease appears to be connected to or triggered by some infections, medications, cancer, and other immune-mediated problems. However, if and how these events cause immune-mediated hemolytic anemia remains unknown, and in the majority of cases, an actual trigger for the whole process is never identified.

This disease is more common in dogs than in cats. In dogs, it occurs more often in females. Cocker spaniels, poodles, springer spaniels, Old English sheepdogs, and Irish setters are affected more often than other breeds. Symptoms range from mild, vague symptoms to severe, life-threatening problems such as respiratory difficulty. Mild symptoms can quickly progress to severe, advanced disease, and a patient with these symptoms needs to be evaluated immediately.

Diagnosis
Anemia (whether immune-mediated or not) can be suspected when the oral mucous membranes (gums and tongue) are paler than normal. A definitive diagnosis of anemia comes from the Complete Blood Count (CBC) which shows a lower than normal red blood cell count (also called hematocrit or packed cell volume). There are many causes of anemia in general, and the results of several tests as well as a complete history and thorough physical exam help to arrive at the diagnosis of immune-mediated hemolytic anemia. Spherocytes are a type of deformed red blood cell that are usually found on a CBC in dogs with IHA but not in healthy dogs.  The presence of spherocytes is strongly suggestive of IHA but their absence does not rule out IHA. An autoagglutination test is sometimes performed to determine if red blood cells clump together, which is a positive indicator of this disease. The Coombs’ test is another test sometimes performed also and reveals if certain molecules are present on the red blood cells’ surface. Other tests may be appropriate for your dog or cat, such as a “tick panel” to evaluate for diseases such as Rocky Mountain Spotted Fever, Ehrlichiosis and Lyme’s Disease. These diseases can be an inciting cause of IHA.

During treatment, one or more of these tests may be repeated to help assess the effectiveness of treatment and to determine if adjustments are necessary. Subsequent test results may also make the long-term course of the disease clearer.

Treatment
Immune-mediated hemolytic anemia is a disease that often begins with a critical, potentially life-threatening crisis, producing symptoms that prompt you to bring your pet in for evaluation. The anemia may be difficult to control, and hospitalization can be necessary for several days in the most serious cases. The more severe cases may even require transfusions.  After this initial period, or else right away in milder cases, oral medications, usually immune suppressants such as steroids, are started and given daily for several weeks to months. 

If it is suspected that your dog or cat is taking medication that might be triggering this disease, we may discontinue it. If an infection is suspected, an appropriate medication is given to treat the infection. Intravenous fluids are often given to control dehydration. Steroids are commonly administered to decrease the excessively active immune system that is destroying the red blood cells. Other immunosuppressive drugs may be given in addition to corticosteroids, if necessary. Whole blood or red blood cell transfusions are sometimes necessary in moderate and severe cases to replace red blood cells that have been destroyed. Oxygen may also need to be given. Because a serious complication of this disease is the formation of blood clots, heparin is sometimes given as a blood thinner (anticoagulant).

Other treatment options are available, depending on how advanced the immune-mediated hemolytic anemia is. Not all of these treatments may be necessary for your dog or cat. We will tailor the treatment regimen for your pet.

Immune-mediated hemolytic anemia is a disease that can respond very well to treatment or that may produce recurrent problems despite treatment. This will vary from one dog to another. With immune-mediated hemolytic anemia, there is always a risk of recurrence, such that affected dogs need to be followed closely with rechecks.

DOs
Give medication exactly as directed. Corticosteroids and other immunosuppressive drugs must be given in gradually decreasing doses when the decision is made to discontinue them. Suddenly stopping them can have severe, life-threatening consequences for your pet.
Inform us of all medications and supplements your pet is taking.
• Limit your pet’s activity level if directed to do so.
Observe your pet closely for any signs or symptoms as this disease may recur weeks to months after your pet is apparently healthy.

DON’Ts
Do not postpone bringing your pet in to us if you observe any symptoms of immune-mediated hemolytic anemia. Prompt diagnosis and treatment may prevent complications that become more severe.
Do not give medication or supplements that you have at home unless directed to do so; some of these may interfere with treatment and cause even more severe problems.

When to Give Us a Call
If you are unable to give medication as directed.
• If your dog or cat has pale gums and is weak or if you suspect a relapse, bring your pet in to us or to the emergency clinic immediately.
If you notice any of the Signs to Watch For listed below.

Signs to Watch For
General signs of illness, which could indicate a beginning (or relapse) of immune-mediated hemolytic anemia. These include vomiting, diarrhea, decreased appetite, changes in behavior such as hiding more than usual, weakness, lethargy, pale gums, exercise intolerance, labored breathing, yellow-tinted gums and/or skin (icterus, jaundice) and dark red/brown urine.
Reduction in symptoms, especially return of appetite to normal and a normal energy level, are significant indicators of improvement.

Routine Follow-Up
Follow-up appointments are always necessary to monitor progress, to determine if treatment should be adjusted or discontinued, and to pursue any abnormalities on previous blood tests. The exact interval varies from dog to dog, but the first recheck typically takes place 1 to 2 weeks after immune-mediated hemolytic anemia is first identified, and then the rechecks are spread out according to how well the problem is regressing.