"Immune Mediated Polyarthritis (IMPA) in dogs explained

"Immune Mediated Polyarthritis (IMPA) in dogs explained

Health & Safety

Some dogs are prone to suffer from a condition known as Immune Mediated Polyarthritis which is an inflammatory disorder that seriously and negatively impacts their joints. When dogs develop the condition, they have trouble walking because of the pain and swelling that occurs within their joints as such, it can be a debilitating disorder.

The Causes of IMPA

The disease is caused by a dog’s immune system not working as it should and as such it fails to send essential white blood cells to their joints. The function of white blood cells is to release enzymes and chemicals into fluids found in joints. Without these fluids, a joint is not protected.

Diagnosing the condition

A vet would want to rule out any other underlying health issues that may be causing the problem which could include the following:

  • Cancer
  • Infection

Both health issues could be triggers that cause swelling in a dog’s joints which is why a vet would want to investigate whether a dog has developed some sort of infection or whether they may have developed cancer. It s worth noting that because a dog’s white blood cells attack their joints when they should not, the condition is often referred to as being an autoimmune disease.

Immune Mediated Polyarthritis is a condition that can develop on its own, but it could also flare up when a dog suffers from other often more severe immune mediated diseases which typically affect other systems.

Symptoms associated with IMPA

Dogs suffering from IMPA put up with swollen, sore joints and as a result the typical symptoms they display are as follows:

  • They are lethargic and unwilling to move
  • They lose their appetites
  • To begin with, dogs develop a mild fever
  • Dogs will only walk when they are forced to and cry out when they move
  • When they move it is like they are walking on hot coals

It is worth noting that when the joints found in a dog’s spine are affected, they will cry out even when touched.

Diagnosing the condition

A vet would thoroughly examine a dog’s joints and check if they have developed a fever. They would typically recommend carrying out certain tests to rule out other underlying causes as mentioned above. The tests a vet would want to carry out are as follows:

  • Taking a full blood count
  • X-rays and other imaging tests
  • Taking fluid from an affected joint for a biopsy

Treatment options

Dogs suffering from the condition would be treated with drugs that calm their immune systems. This could involve giving them steroid drugs. As such, a dog would need to be closely monitored during their therapy to make sure the dosages are correct and to establish how a dog is responding to the treatment. There are known side effects to the use of steroid drugs which includes increased thirst and urination. It is also worth noting that some dogs that suffer from immune mediated polyarthritis often need to remain on medication for the remainder of their lives whereas others that respond well to the treatment can come off them altogether.


As a rule of thumb, most dogs suffering from IMPA go on to lead full lives and have a good quality of life providing the condition is diagnosed and treated early enough and before too much damage has been done to their joints. However, as previously mentioned some affected dogs need to be given specific medication for the rest of their lives when they suffer from immune mediated polyarthritis, but in all cases a dog’s condition should be closely monitored by a vet.

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