Autoimmune Hemolytic Anemia in Dogs

It is important to know when your dog needs to be seen by a veterinarian as soon as possible. Breathing problems, bleeding, and collapse are all reasons that seem inherent to most pet owners. 

However, certain signs of a serious illness can be as subtle as a change in gum color. If your dog’s gums are pale pink or white, this may be a sign that your dog is anemic.

Anemia refers to the lack of sufficient oxygen molecules being supplied to the body via the bloodstream.Red blood cells make up about 40 to 45% of your dog’s total blood volume, and they are able to carry oxygen to other parts of the body as blood flows towards them. A protein on red blood cells known ashemoglobin is responsible for binding oxygen to the red blood cells.

In a condition where your dog has lost blood (e.g. trauma or surgery), he may not have enough red blood cells to carry oxygen, so he subsequently becomes anemic. Disorders such as heart disease, liver disease, and kidney failure can also result in anemia.

Bone marrow disorders cause anemia because the bone marrow is responsible for the production of new red blood cells. Diseased bone marrow cannot make enough red blood cells to meet demand.  

Autoimmune disorders are diseases where the immune system targets and destroys the body’s own tissues instead of infectious or foreign agents.Autoimmune or immune-mediated hemolytic anemia means that the immune system attacks red blood cells and causes them to become very fragile orfriable. 

As a result of this fragility, red blood cells end up rupturing or bursting, resulting in anemia due to a lack of sufficient red blood cells in circulation. The rupturing of red blood cells is known ashemolysis.

Healthy bone marrow will still produce red blood cells, but the lifespan of the red blood cells is now shorter because of their fragility. In most cases, when blood cells are examined on a microscope slide, your vet may notice lots of immature red blood cells known asmetarubricytes or nucleated red blood cells. 

This is a sign that your dog’s anemia isregenerative because bone marrow is working overtime to produce new red blood cells and releases newer red blood cells into circulation much faster. Regenerative anemias are consistent with a diagnosis of immune-mediated hemolytic anemia (IMHA).

In almost 75% of cases, a specific cause for IMHA will not be apparent. This is known asprimary or idiopathic IMHA. For some unknown reason, dogs will incorrectly make antibodies that target and destroy their own red blood cells.

In secondary IMHA, a different disease process will affect the outer layer of the red blood cells and cause them to “appear” different or foreign to your dog’s immune system. This results in an autoimmune response. Toxins, allergic or drug reactions, blood parasites, snake bites, infectious agents like tick-borne illnesses, and even cancer have all been cited as reasons for IMHA in dogs.

One of the classic signs of anemia in dogs is an unusual gum color. Normal healthy dogs have bright “bubblegum” pink gums, but anemic dogs have gums that are pale pink or even white. If there is concurrent liver disease, gum color can have a bright yellow or orange color.

Because anemic pups aren’t getting enough oxygen to the rest of their body, they are often listless and tired. Their bodies try to catch up by causing increased respiration and panting, and their hearts may pump faster to get more blood to the rest of the internal organs.

When red blood cells rupture, hemoglobin is released into the bloodstream and are cleared from the body through the kidneys. As a result, your dog’s urine may appear dark brown or the color of port wine.

Dogs with IMHA can also have signs of gastrointestinal upset. Vomiting, diarrhea, and lack of appetite are all possible clinical signs.

Treatment is usually targeted on supportive care and treating the underlying cause. If your dog’s red blood cell volume orpacked cell volume is less than 13%, he will need a life-saving blood transfusion. Without one, dogs can become unstable very quickly. 

Fluid therapy is also recommended to help replenish fluid volume in your dog’s body, and it can also help in the event of a transfusion reaction. These are rare but life-threatening occurrences.

If a tick borne-illness is suspected, your vet may prescribe an antibiotic like doxycycline. If toxin ingestion is confirmed, an antidote or supportive care will be necessary. If a cause cannot be determined, steroids are often prescribed. Prednisone is often prescribed at higher-doses in order to reduce inflammation and suppress the immune system. A faster response can be achieved with concurrent use of an immunosuppressive drug like cyclosporine, azathioprine, or mycophenolate.

Prognosis will be based on the underlying cause and response to therapy. It can take several months before you can successfully wean your dog off of immunosuppressive medications. Also, your dog should avoid all future vaccinations because they can increase the risk of an immune reaction that can trigger IMHA once more.

It is important to know the signs of anemia in dogs. There are numerous causes, but IMHA is life-threatening and can be tricky to diagnose if a cause cannot be identified. However, most dogs with this kind of IMHA tend to respond well to steroid and immunosuppressive drug therapy.

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