Immune Mediated Polyarthritis


Why Should I Bring my Dog with Suspected Polyarthritis to Willows?

Willows is one of Europe’s leading small animal referral centres. Our state-of-the-art hospital is led by internationally renowned Specialists, committed to providing the highest standards of veterinary care. At Willows, our multi-disciplinary team includes Specialists in the fields of Orthopaedics, Internal Medicine, Diagnostic Imaging and Anaesthesia, all of whom may be involved in the diagnosis of patients with immune-mediated polyarthritis.

Our clinicians are always on hand to provide care and support to patients with this condition, as well as their owners. Willows is also involved in a number of scientific studies into IMPA and so our Specialist are very much at the forefront of management of this disease.


What is Immune-Mediated Polyarthritis?

Immune-mediated polyarthritis (IMPA) is a disorder of the immune system (which normally fights off infections) leading to inflammation in multiple joints. This condition in dogs, is similar to rheumatoid arthritis in people. Immune-mediated polyarthritis is different to degenerative joint disease (i.e. wear and tear arthritis or osteoarthritis) which occurs much more commonly in dogs after injuries or due to old age.

The immune system is usually responsible for fighting infections in the body (e.g. caused by bacteria and viruses). In polyarthritis, the immune system becomes over-activated and starts to attack the tissues of the joints. The immune system can sometimes be ‘tricked’ to over-react in this way when there are diseases present in other parts of the body, including infections, cancer or gastrointestinal disease.


What are the Most Common Signs of Immune-Mediated Polyarthritis?

Arthritis in a joint causes pain, stiffness and lameness. Dogs with polyarthritis have inflammation affecting joints in more than one limb, and so they appear very stiff, reluctant to move and they may be lame in different limbs at different times. Dogs with this condition can also have vague signs such as lethargy and a poor appetite.

On examination by a Vet, dogs with polyarthritis are usually found to have stiff, painful and swollen joints in more than one limb. They may also have neck and/or back pain (because the entire spine contains a series of joints between the vertebrae). Many dogs with polyarthritis have a fever, and in some dogs this is the most significant finding on veterinary examination.

How is Immune-Mediated Polyarthritis Diagnosed?

After taking a full history and performing a thorough examination, a diagnosis of polyarthritis is made by taking joint fluid samples from multiple joints and submitting them for laboratory examination. Sampling the joint fluid is usually performed under sedation or a general anaesthetic. X-rays may also be taken of some of the joints to check for any changes suggesting bone damage secondary to the chronic inflammation.

The next step in the investigation of polyarthritis is to look for any possible underlying trigger factors for this disorder. This step is likely to include blood and urine tests, chest x-rays, abdominal ultrasound scanning or CT scans.


What Treatments are Available for Immune-Mediated Polyarthritis?

Polyarthritis is usually treated with the use of medications to suppress the over-active immune system. This includes the use of steroids and other similar medications, sometimes in combination. These medications can have side effects which will be discussed with owners and monitored carefully as the treatment goes on, through examinations and blood tests. Most dogs with immune-mediated polyarthritis are treated for several months with immune-suppressive medications, but the doses of the drugs are gradually reduced over that time.

What Can I Expect if my Pet is Treated for Immune-Mediated Polyarthritis?

Most dogs that are treated for polyarthritis respond to treatment and are usually much brighter and more comfortable on medication. Some dogs with polyarthritis experience a flare-up when the doses are reduced or the medications are stopped, and these dogs may need long term (sometime lifelong) treatment.

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Internal Medicine

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To assist owners in understanding more about Internal Medicine we have put together a range of information sheets to talk you through the some of the more common Medicine conditions seen and treated by our Specialists.