Reviewed by Sara Ochoa, DVM
Evans syndrome is a complex autoimmune disease where the immune system attacks and destroys a dog’s red blood cells and platelets.
This abnormal immune response can be either primary (no known cause) or secondary. Most dogs with this disease fall under the “primary” category.
Has your dog been diagnosed with Evans Syndrome? If so, it can be confusing and difficult to understand. In this post, we breakdown the differences between the two specific blood disorder, including:
- the complications that can occur
- treatment options
- prognosis/life expectancy
Any dog can be affected, but it primarily affects middle-aged female dogs. Sadly, owners need to be prepared for this labor-intensive, expensive, and sometimes lifelong condition.
Evan Syndrome – The Breakdown of a Complex Disease
In order to understand Even Syndrome, it’s important to explain the two different blood disorders that come with the diagnosis.
Evan’s syndrome is sometimes referred to as the “evil big brother” of IMHA and ITP. A dog can have either of these conditions to varying degrees. However, the real risk is when the two conditions come together and cause the perfect storm.
Evan’s syndrome is a serious and sometimes life-threatening condition. It occurs with the combined immune mediated destruction of red blood cells (IMHA) and platelets (ITP).
Unfortunately, this disease tends to be diagnosed once the dog is in critical condition. At that point, it’s thought that if the dog can make it past the first 3 days, he/she has a good chance of recovery.
Dogs with Evan’s syndrome are at risk of spontaneous bleeding and extreme anemia.
Immune-mediated hemolytic anemia (IMHA)
If your dog was diagnosed with IMHA, it means that the immune system attacks the pet’s own red blood cells. Basically, it treats the red blood cells as if they were a foreign bacteria or virus.
Unfortunately, this happens so quickly that the red blood cells are not able to regenerate fast enough to replace the ones that are lost. This causes severe anemia. With anemia comes lack of oxygen delivery through the body.
IMHA can affect dogs and cats. However, it’s mostly middle-aged female dogs that are affected. This blood disorder can occur due to primary or secondary causes.
Sadly, IMHA commonly causes secondary conditions in affected patients. Lack of oxygen circulation can affect internal organs including the liver and kidneys. Blood clots can form within the organs and cause severe breathing difficulties and sometimes sudden death.
Immune-mediated thrombocytopenia (ITP)
ITP is not as common in dogs. With this condition, the dog’s immune system destroys platelets in the body.
Veterinarians will look for reasons for anemia and low red blood cell counts. In dogs, they may look for tick-borne disease/infection or cancer.
Both conditions above can be considered Primary (unknown underlying cause) or Secondary.
Primary Evan’s Syndrome in Dogs
Primary IMHA in dogs is considered idiopathic (unknown underlying cause) when no other medical reason is present. Essentially, this is a diagnosis made by the exclusion of other medical possibilities.
Primary immune-mediated thrombocytopenia is the most common in dogs.
Secondary Evan’s Syndrome in Dogs
Dogs who present to the veterinarian with anemia may be suspected of having secondary IMHA.. This is true if the dog has an infection, cancer, is on new medications, or has recently had a vaccination.
This is because medications and some vaccines could stimulate the immune system.
Sometimes, this increased stimulation paves the way for things to get out of balance. When the normal functions of the body (in this case the red blood cells) turn on themselves, it’s known as an autoimmune disorder.
Secondary causes of ITP or IMHA in dogs can include:
- tick-borne disease
- bacterial infections
- infectious disease
- other autoimmune conditions including systemic lupus erythematosus
Symptoms of Evan’s Syndrome in Dogs
Dogs often have no symptoms of the disease. It’s only on routine blood tests when a low platelet count is observed. If the dog is showing signs of the condition, he/she may have:
- Mucosal Bleeding
Pets with IMHA typically present with signs of:
- depressed appearance
- pale white mucous membranes
- heart murmur
Signs of Internal Bleeding Include:
Internal bleeding cannot be seen, but are very serious. Dogs with this condition can present with clinical signs of bleeding including:
- tiny spots on the skin that signify bleeding (petechiae)
- gingival bleeding
- dark, sticky feces (melena)
- nosebleeds (epistaxis)
- scleral and retinal bleeding
- blood in stool (hematochezia)
- vomiting blood (hematemesis)
- bloody vaginal discharge
- blood inside the front of the eye (hyphema)
- blood in the urine (hematuria)
Diagnosis of IMHA in Dogs
Complete Blood Count
A complete blood count (CBC) can reveal low levels of red blood cells, platelets, and white blood cells.
Direct Antiglobulin Test (DAT)
This test determines whether the number of antibodies is higher than normal.
This test, also known as the Coomb’s test, can detect whether antibodies are attached to the dog’s red blood cells. In doing this, the test can detect whether the dog has become anemic.
Bone Marrow Biopsy
Can can trigger autoimmune disorders. If the dog has, or is suspected or having cancer, a bone marrow biopsy may be recommended.
On physical examination, the veterinarian will check for signs of pain, fever, and swollen lymph nodes. He/she will look for pale gums, signs of dehydration, and will listen to respiration and heart rate.
Infectious Disease Titers
When screening for secondary causes of Evan’s Syndrome, infectious disease titers may be administered. These are special blood tests that check to see if a dog is immune to specific disease.
Dogs are also assessed for tick-borne disease (bacterial infections).
This test helps to determine how normally the blood clots.
This non-invasive test uses sound waves to create images of internal organs and structures. It is often used in combination with chest x-rays to identify underlying disease.
The Anti-nuclear Antibody titer are used to evaluate for immune response against red blood cells and the genetic material of the cell itself.
Treatment Options for Dogs with IMHA
Thankfully, IMHA is treatable. However, treatment is generally aggressive and expensive.
Initial treatment usually happens during the acute stage of the condition. This is because pet owners may not realize there is a problem until the dog becomes very sick.
Most dogs must be hospitalized in order to treat the anemia. Types of treatment involved can include:
Dogs with Evan’s syndrome are treated with steroids that act as immunosuppressive agents. These medications may include prednisone.
Steroids are considered the first-line therapy option in dogs with Evan’s syndrome.
Cyclosporine A (CsA) is used in combination with corticosteroid treatment. These immunosuppressive drugs helps lower the immune-response to better fight infection.
This is another type of immunosuppressive agent that can help lower the immune system attack response.
Aspirin & Heparin
These drugs may be used to help prevent blood clot formation.
This type of blood transfusion is provided with whole blood, concentrated red cells or hemoglobin concentrates.
The goal of intravenous immunoglobulin therapy is to normalize a compromised immune system.
Treatment of Secondary Disease
Patients may require medication to treat underlying infection or disease. For example a dog with secondary evan syndrome who has cancer, may also require chemotherapy, surgery, etc.
Supportive care includes things like fluid therapy (intravenous fluids), observation, repeat blood count tests, etc.
Breeds At Risk of Developing Evan’s Syndrome
Although this condition can occur in any dog or any age, there are a few breeds that appear to have a higher genetic predisposition. These include:
- Middle-aged dogs
- Cocker Spaniels
- German Shepherds
- Old English Sheepdogs
- Miniature Schnauzers
The High Cost of Treating Evans Syndrome
A dog presenting with the clinical signs of Evans syndrome is usually in a critical and dangerous phase. This may mean a lengthy hospital stay of up to 10 days or more.
Factor in the cost of medications, supportive therapy, and the cost of diagnostic tools used, supplies, doctors, nurses, technician support and more.
The grand total? It depends on the dog and the clinic, but you could be looking at a vet bill of over $10,000 or more.
Life Expectancy of a Dog with Evans Syndrome
By the time a dog is diagnosed with Evans Syndrome, he/she will likely be in serious and life-threatening condition.
According to a case report published in a Turkish veterinarian magazine, “many studies describe high mortality rates during the first 2 – 3 weeks of treatment”. Unfortunately, Evan’s syndrome as a high mortality rate.
According to the Kentucky Veterinary Medical Association, up to 80% of dogs diagnosed with Evan’s syndrome recover well enough to be released from hospital. Unfortunately, the dog will require a lifetime of drug therapy.
This will involve frequent visits to the veterinary clinic to monitor serious side-effects of the medication. Dosage adjustments may also be necessary.
Dogs with Evan’s syndrome may experience periods of fatigue and weakness over time. Unfortunately, dogs are usually already at a critical, acute phase when they are diagnosed.
The mortality rate for dogs with Evan’s syndrome varies. However, it’s important to understand that the initial treatment plan must be very aggressive in order to save the dog.
Treatment usually involves a variety of options that help to calm the over-active immune response, stop internal bleeding, and manage any secondary infections or disease.
I want to thank you for reading this post. Please continue returning to Your Dog’s Health Matter for more informative posts.