What is immune-mediated polyarthritis?

In this case, poly refers to this condition affecting more than one joint of your dog. The immune-mediated part of the name refers to the fact that your dog’s immune system is directly responsible for the problem. This condition comes in two forms; non-erosive and erosive. Since non-erosive is the most common form of polyarthritis in dogs, that is what we are going to discuss today.

The causes of immune-mediated polyarthritis

As we mentioned above, the direct cause of polyarthritis is your dog’s immune system. As I am sure you’re aware, the immune system responds to infection. However, your dog contracting immune-mediated polyarthritis (IMPA) doesn’t mean that they have an infection in their joint. In fact, the total opposite is true. In all cases of IMPA, there are no infections within the joints at all. Having said that, something happens somewhere in the body that does kickstart the antibody response. Those antibodies enter the joint via the joint fluid and begin a chemical reaction that leads to the swelling of the joint.

The list of causes for polyarthritis is extensive. Infection elsewhere in the body can certainly be responsible, but it can also be a response to:

  • Physical trauma
  • Drugs
  • Vaccines
  • Cancers
  • Systemic lupus erythematosus

There is also breed associated polyarthritis that affects Akitas and other breeds. If none of these are the cause of the arthritis then it will be classified as idiopathic, meaning the vet doesn’t know the cause.

The symptoms of IMPA

If your dog develops immune-mediated polyarthritis after another disease, the symptoms may be very different to the ones described below, but dogs with this condition can have the following symptoms:

  • Lethargy
  • Fever
  • Weight loss/loss of appetite
  • Be reluctant to move
  • Lameness
  • Stiffness
  • Joint pain and swelling

It’s critical for you to realise that not all dogs will develop all, or any, of these symptoms. Meaning it can be difficult to diagnose polyarthritis. If you notice that your dog isn’t behaving as normal, make an appointment with a vet. Even if they have a condition already that might be responsible for their behaviour, get them check out.

How is polyarthritis treated?

Because of what this condition does and the causes of it, the treatment for polyarthritis is usually immunosuppressive drugs. These drugs typically need to be taken for a long period of time and the first treatment may need to be a higher dose than normal for the initial effect. It is crucial that your dog’s vet rules out any other form of arthritis before they begin treatment. If they don’t, they can make other forms of arthritis worse. Once your dog begins its treatment for immune-mediated polyarthritis, they will have to be monitored carefully to ensure that the treatment has no adverse effects.

If your dog has this condition and you have questions about it, please ask your dog’s vet. They’re always the best resource for information about your dog and their health and wellbeing. If you would like to find out more about other forms of arthritis, we have plenty of articles on here that might be of use to you.

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