Polyarthritis is a condition that affects multiple joints in the body. There are many different types of polyarthritis, but one type particularly common in dogs is immune mediated polyarthritis. Immune mediated polyarthritis in dogs occurs when the body's immune system mistakenly attacks the cells in the joints, causing inflammation and pain. While there is no cure for immune mediated polyarthritis, there are treatments that can help manage the condition and improve your dog's quality of life.

What is immune mediated polyarthritis in dogs?

Immune mediated polyarthritis in dogs is an autoimmune condition that causes inflammation in the joints. The immune system is responsible for protecting the body from foreign invaders, but in some cases, it can mistake healthy cells for harmful invaders. When this happens, the immune system will attack these cells, causing inflammation. In immune mediated polyarthritis, the immune system attacks the cells in the joints, causing pain, stiffness, and swelling.

What are the causes of immune mediated polyarthritis in dogs?

There are 4 types and causes of immune mediated polyarthritis in dogs:

Idiopathic polyarthritis: Idiopathic or primary disease is the most common type of immune mediated polyarthritis in dogs, making up approximately 65% of cases. There is no known cause for the idiopathic disease.

Reactive polyarthritis: Dogs with reactive or secondary polyarthritis often have systemic diseases, such as gastrointestinal disorders, pancreatitis, bacterial infections, viral infections, systemic fungal infections, or they may be taking certain medications such as sulfonamides.

Systemic lupoid erythematosis (SLE): Dogs with SLE produce autoantibodies against various cell structures, which results in the formation of high levels of immune complexes. Multiple organs are affected by this condition, including the skin, joints, kidneys and central nervous system.

Breed-Associated Polyarthritis: There is a theory that polyarthritis occurs in certain breeds of dogs such as the Akita, Boxer, Weimaraner, and Bernese Mountain dog, which is caused by genetics.

What are the symptoms of immune mediated polyarthritis in dogs?

The most common symptom of immune mediated polyarthritis is shifting lameness. This can be mild, moderate, or severe, and may affect one or more limbs but in most dogs, all 4 limbs are affected.

Other symptoms may include:

  • Difficulty walking or standing
  • Joint stiffness
  • Swelling in the joints
  • Loss of appetite (anorexia)
  • Fever

How is immune mediated polyarthritis in dogs diagnosed?

A diagnosis of immune mediated polyarthritis in dogs is based on the exclusion of other potential causes. Signs and symptoms that suggest inflammation in more than two joints, along with fluid from those joints being clear or containing mostly neutrophils, are indicative of this condition.

Your veterinarian will start with a detailed physical examination and a thorough medical history of your dog. They will then likely recommend some or all of the following tests:

Serum biochemistry profile: This test measures levels of enzymes and proteins in the blood. It can help to rule out other conditions that may cause similar symptoms.

Arthrocentesis: In this test, a needle is inserted into the joint and fluid is withdrawn for analysis. This can help to determine if immune mediated polyarthritis is the cause of the inflammation.

Imaging: X-rays or MRI may be recommended to assess the condition of the joints and look for any damage that may have occurred.

How is immune mediated polyarthritis in dogs treated?

There is no cure for immune mediated polyarthritis in dogs, but there are treatments available that can help to manage the condition and improve your dog's quality of life. Treatment options include:

Nonsteroidal anti-inflammatory drugs (NSAIDs): NSAIDs may help with milder cases of immune mediated polyarthritis, but most dogs will require corticosteroids or other immunosuppressive drugs. If NSAIDs don't work well enough, treatment with corticosteroids is delayed until a washout period is completed between the two medications.

Immunosuppressive therapy: This is the most common treatment for immune mediated polyarthritis in dogs. The goal of therapy is to suppress the immune system enough to reduce inflammation, while not causing serious side effects. Cyclosporine and corticosteroids (e.g. prednisone) are examples of common drugs used.

Doxycycline trial: In places where tick-borne polyarthritis is prevalent, veterinarians may recommend trying doxycycline before starting immunosuppressive therapy. If a positive response is noted within 7 days, treatment should be continued for 28 days.

Melatonin: There are some anecdotal reports that melatonin may help with immune-mediated diseases in dogs. There is no definitive evidence however that melatonin is effective or safe for dogs with immune-mediated disease, but experimentally it has been shown to have an immunomodulating effect on the immune system.

What is the prognosis for dogs with immune mediated polyarthritis?

If the trigger for a dog's idiopathic immune mediated polyarthritis is identified and removed, most dogs respond well to treatment and the disease does not recur. However, in some cases, arthritis may continue indefinitely unless treated long-term, or it may recur as therapy is tapered or terminated.

In conclusion, immune mediated polyarthritis in dogs is a condition that causes inflammation in the joints. It is a serious condition that can be debilitating for dogs, but fortunately, there are treatments available that can help to improve your dog's quality of life. If you have any further questions or concerns, please do not hesitate to speak with your veterinarian.