Evans Syndrome in Canines: An Examination by Rhiannon Koehler, DVM, MPH, Reviewed by Brittany Kleszynski, DVM on 03/28/2025, Published on 03/31/2023.
In 1951, Dr. Robert Evans and associates delved into the mysterious world of autoimmune disorders, focusing on their impact on red blood cells and platelets in humans and our beloved pets. This groundbreaking research ultimately led to the first diagnostic criteria for Evans Syndrome, a condition that, while not common in canines, can be life-threatening when it occurs.
Let's shed some light on this pesky condition that can afflict our four-legged friends. We'll break down what Evans Syndrome is, symptoms to watch out for, and potential treatment methods.
What Is Evans Syndrome?
Evans Syndrome appears when a dog's immune system takes a turn for the worse, recklessly attacking and destroying both its red blood cells and platelets. This rampage leaves the dog vulnerable to severe anemia and spontaneous bleeding.
When the immune system only attacks red blood cells, the result is a condition called immune-mediated hemolytic anemia (IMHA). On the other hand, when the immune system targets only platelets, it leads to immune-mediated thrombocytopenia (IMTP). Evans Syndrome occurs when both IMHA and IMTP occur simultaneously.
In the bewildering world of Evans Syndrome, damaged cells are swiftly whisked away by the liver and spleen, posing a significant threat to the dog's health.
This medical emergency demands immediate attention! Veterinary care is essential, so don't hesitate to act if you suspect Evans Syndrome.
Causes of Evans Syndrome in Dogs
Evans Syndrome may strike without warning (primary or idiopathic), or it could be triggered by a specific underlying condition (secondary).
Potential secondary causes include:
- Tick-borne diseases: Diseases transmitted by ticks can spark Evans Syndrome.
- Cancer: It's believed that cancer may play a role in some cases of Evans Syndrome.
- Recent Vaccination: In some cases, vaccinations may initiate an immune response that targets the dog's own cells.
- New Medication: Certain medications can provoke an immune response leading to Evans Syndrome.
In some instances, genetics might play a role. Dog breeds more susceptible to Evans Syndrome include Cocker Spaniels and Old English Sheepdogs. However, any breed of dog, including mixed breeds and those with no family history, can contract Evans Syndrome.
Symptoms of Evans Syndrome
Dogs experiencing Evans Syndrome are usually in a pretty rough shape, so if you notice any of these warning signs, get your pet to an emergency veterinarian ASAP:
- Pallor: **Pale gums, eyes, and genitals
- Fatigue and Weakness
- Increased Breathing Rate
- Bruises or Bleeding
- Nosebleeds and Bleeding from the Mouth
- Blood in Urine or Stool
- Collapse
With Evans Syndrome, you'll often observe symptoms of both anemia and bleeding or bruising.
Diagnosing Evans Syndrome in Dogs
The emergency veterinarian will assess your pet thoroughly. If they suspect Evans Syndrome, they'll want to:
- Check for Bruising, Pallor, and raised Heart Rate
- Inspect Blood Under a Microscope
- Perform a Urinalysis
- Test Coagulation
- Slide Agglutination Test
- Direct Coombs Test
- Test for tick-borne diseases
- X-rays and Ultrasound Examination of the Chest and Abdomen
Your pet's CBC would show low red blood cell numbers, low platelet numbers, and potentially high white blood cell numbers. On review of a microscopic slide, the veterinarian may notice abnormal platelet counts, small red blood cells (spherocytosis), and the release of young red blood cells (reticulocytosis).
Your pet's lab work may also reveal elevated liver enzymes due to the stress of anemia on the organs.
Treatment for Dogs with Evans Syndrome
Treatment for Evans Syndrome typically involves hospitalization, fluids, supportive care, and blood transfusions. Steroids like dexamethasone are often used, along with other medications to modulate the immune system and halt attacks on the dog's own cells.
If your dog has an infection, specific antibiotics will be prescribed. Even if tests for tick-borne diseases come back negative, some veterinarians may prescribe doxycycline to cover all bases.
In severe cases, a low dose of the chemotherapy agent vincristine can be administered intravenously to accelerate the return of appropriate platelet levels.
To manage stomach and intestinal bleeding, medications like omeprazole and sucralfate may be prescribed to reduce ulceration and protect the stomach and esophagus.
If Evans Syndrome is caused by an underlying cancer, treatments aimed at the cancer itself may be necessary.
In the most severe cases, the veterinarian may recommend plasma exchange or plasmapheresis to cleanse the blood of destructive immune chemicals while preserving red blood cells and platelets.
When it comes to the survival rate of Evans Syndrome in dogs:
- Dogs who survive the first few days and are discharged generally have good long-term prognoses.
- Pets with secondary Evans Syndrome have a variable prognosis, depending on the underlying cause.
Long-term management of Evans Syndrome may require immunosuppressants for life. Close collaboration with the veterinarian will determine the lowest effective dose to maintain long-term control.
Tapering medications too soon or too rapidly could lead to relapse, which is often more severe than the initial onset.
After surviving Evans Syndrome, you'll probably need to avoid vaccinations for the future. Pet health insurance can help protect you financially should Evans Syndrome arise.
Lastly, the cost of treating Evans Syndrome can vary but may range from several thousand to over $10,000 for hospitalization, testing, and medications.
The rampage of Evans Syndrome in dogs, a chronic condition that affects both red blood cells and platelets, is rooted in the faulty behavior of the immune system, as understood through scientific research in the field of pet health and medical-conditions.
Proper understanding and effective management of Evans Syndrome can be accomplished through awareness of its causes, symptoms, and potential treatment methods, all of which contribute significantly to the overall health-and-wellness of affected pets.
