Immune Mediated Polyarthritis (IMPA)

Introduction to Immune Mediated Polyarthritis

Immune Mediated Polyarthritis is a condition in which the immune system makes a mistake and starts to attack the joints. This can cause fever, pain and lameness. Often the lameness will shift from limb to limb or dog’s will appear to be “walking on eggshells.” Other diseases, such as tick borne disease and joint infections can look similar, and therefore diagnostics are recommended to ensure the diagnostics. IMPA may also sometimes be associated with inflammation of the covering of the spinal cord and/or brain- which is called meningitis.

Symptoms of iMPA

Please contact your veterinarian if your pet develops new symptoms or if existing symptoms seem to be getting worse. Symptoms include:

Pain not controlled by medications
Difficulty walking
Seizures
Change in behavior
Reluctance to eat or drink
Vomiting or diarrhea

Diagnosing IMPA

IMPA is diagnosed by obtaining fluid from multiple joints and sending it to the lab. We will also culture this fluid, and often also run a panel looking for tick borne disease. It can take up to a week to get this testing back.

Will my pet be okay?

These diseases are treatable. Most dogs will do well, becoming normal in the first month of treatment. We very slowly lower their drug doses over a period of about 4 to 6 months. Ideally, before we stop drugs entirely, we will repeat joint taps. Some dogs do need a small amount of medication lifelong. Very rarely a patient does not respond to therapy.

Treatment of IMPA

There are a lot of different treatment regimens that can be used to treat IMPA, but most involve using a type of steroid, for instance prednisone or dexamethasone. Some pets will also be placed on a second medication to help control the immune system if their symptoms are not controlled on steroids alone or if they cannot tolerate steroids. This second medication lets us use less steroid over time, which is helpful because steroids can have side effects when used long term and/or at high dose. Examples of the second medication that your veterinarian might recommend include mycophenolate, cyclosporin, azathioprine, and leflunomide. Your pet will be less able to fight infections on these drugs and vaccination may not be recommended.

Regular check ups with your veterinarian will be important in monitoring your pet’s health, especially early on. Dr. Jurney usually rechecks her patients 1-2 weeks after the initial diagnosis and then monthly for the first several months. If your pet is doing well, often we will do every other recheck by telemedicine. Further recheck schedules will be dependent on how severely your dog is affected.