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Evans Syndrome In Dogs: Causes, Signs & Treatments

Written by: Dr. Ernie Ward

Last Updated on March 15, 2024 by Dogster Team

Evans Syndrome In Dogs: Causes, Signs & Treatments

I was rushing into the lobby to help a sobbing pet parent cradling an unresponsive Cocker Spaniel. As I took the dog out of her arms, I began immediately scanning for vital signs: pulse — weak and thready; respiration — faint but regular; muscle tone — limp; gums — yellow and dry; eyes — dilated and yellowish sclera. I already had an idea of what might be wrong.

“No, no medication or supplements. I haven’t fed her anything other than her regular food and treats. She hasn’t been around any other dogs, and I give her a heartworm pill promptly each month. She started acting a little more tired and not wanting to go for her walk a few days ago, but it’s been so hot. I didn’t see her get in the trash, but why else would she be so yellow?”

Life-threatening condition

CoCo was a 6-year-old, spayed Cocker Spaniel with a textbook, terrific dog mom. I knew time was running short, so I got straight to the point.

I was worried about a life-threatening condition called Immune-mediated Hemolytic Anemia or IMHA. The yellow color of her eyes and gums, called icterus, was likely due to red blood cells being hemolyzed or destroyed. This had caused a severe loss of blood, known as anemia, and was making her weak. I needed to do blood tests to verify my hunch.

As I waited for my veterinary technicians to run the tests and prepare for emergency treatments, I examined a blood sample under the microscope. I was searching for a specific type of blood cell called a spherocyte. If a dog has both icterus and spherocytes, that’s pretty much all I need to diagnose IMHA in an emergency.

After an agonizing 30 seconds, I found what I was looking for. Mean-
while one of my veterinary technicians was finishing another IMHA test called a saline agglutination test. As soon as I looked up from my microscope, we both said, “IMHA.”

IMHA is a somewhat uncommon condition in which the body’s immune system attacks and removes its own blood cells, resulting in life-threatening anemia, kidney damage, and blood clots. In about 70% of cases, it is fatal. It tends to affect young to middle-aged dogs, more commonly females, and Cocker Spaniels are much more likely to develop IMHA than any other breed. Miniature Schnauzers, Collies, Springer Spaniels, Poodles, Bichons, Miniature Pinschers, Sheepdogs, and Maltese are other breeds at increased risk.

The majority of dogs, 65 to 70%, have primary or idiopathic IMHA, which means we don’t know what caused it. Evans syndrome is an even more deadly variant in which both the red blood cells and platelets are being attacked. Symptoms of both usually begin with gradual weakness and lethargy, progress to decreased appetite and depression, and eventual collapse and icterus (yellow discoloration). Some dogs will experience darker than usual urine and dark or bloody stools. In some cases, a dog is perfectly fine one day and fighting for their life the next. IMHA is a diagnosis no veterinarian wants to make.

sick rottweiler dog at a veterinary clinic
Image Credit: Vera Larina, Shutterstock

Immediate treatment

IMHA requires immediate medical treatment. Too often I’ve been faced with a patient who had been sick for a week or more, and there’s simply too much damage and too little remaining red blood cells to save them.

The primary goals are to stop the immune system from destroying red blood cells and prevent blood clots, replace the lost blood, and prevent further bleeding. The foundation of treating IMHA is a blood transfusion. Next, the attacking immune response is shut down by administering corticosteroids, often combined with azathioprine, a drug typically used to prevent organ transplant rejection. Because blood clots are a significant risk in IMHA cases, drugs such as ultra-low-dose aspirin are often given to reduce platelet aggregation. Aspirin can be toxic to dogs, even in low doses, so never give it without your veterinarian’s specific advice.

Some veterinarians will perform emergency surgery to remove the spleen, and that’s exactly what I was planning for CoCo. Surgery in critical cases is always a risk, but CoCo’s mom and I agreed in her case it was her best chance of survival.
CoCo survived surgery and was placed on long-term steroid treatment. I’m happy to say she was in the 50% that survived IMHA beyond one year. I’m sad to share that she passed about 20 months after that fateful Monday morning. The fact is that IMHA is often a lifelong battle, and eventually, CoCo had a severe relapse and passed away within 48 hours. I’m happy CoCo was able to enjoy a fairly normal life for an additional year and a half, and her mom said she wouldn’t trade a day.

The take-home message is don’t delay seeing your veterinarian when your dog “just isn’t right.” CoCo’s mom sought treatment as early as possible, and we were able to beat IMHA, at least for 20 months. IMHA and Evans syndrome, along with any immune-mediated condition, worsen rapidly and early intervention is the best shot at a successful outcome.

Featured photo Credit: vchal | Getty Image

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