Immune-mediated Polyarthritis in Dogs

Overview of Canine Immune-mediated Polyarthritis

Immune-mediated joint disease is a condition in which the immune system is stimulated to cause an inappropriate inflammatory response in one or usually multiple joints. The condition is sometimes termed idiopathic immune-mediated polyarthritis, reflecting an unknown cause of the condition that involves multiple joints.

Inflammation of the lining of the joints causes an increase in white blood cells in the joint fluid. This causes joint swelling and pain.

As with most diseases of the immune system, female animals are at increased risk of getting the disease. The disease is also most commonly seen in younger to middle-aged animals. All breeds may be affected.

What to Watch For

Signs of immune-mediated polyarthritis in dogs may include:

Diagnosis of Immune-mediated Polyarthritis in Dogs

Treatment of Immune-mediated Polyarthritis in Dogs

Home Care and Prevention

Carefully monitor your dog for improvement or deterioration. Dogs tend to respond to therapy quickly, but relapses may occur, especially as drug dosages are decreased. Drugs need to be slowly decreased over time. Careful communication with your veterinarian is essential.

Dogs on immunosuppressive therapy are more susceptible to infection and need to be monitored closely for changes in behavior, appetite or general condition. Periodic blood tests are needed when animals are on certain immunosuppressive drugs.

Initially, strict rest is recommended, but as your pet improves, normal activity may resume.

There are no known measures that can be taken to prevent the occurrence of immune-mediated joint disease. Knowledge of what breeds may be at risk and the associated clinical signs may allow for earlier diagnosis.

If your pet has had immune-mediated disease, future vaccinations should be used with caution. An appropriate vaccination schedule should be discussed with your veterinarian.

In-depth Information on Immune-mediated Polyarthritis in Dogs

Idiopathic immune-mediated polyarthritis is caused by an abnormal immune system response. The joints of one, or typically, multiple joints are identified as abnormal and an inflammatory reaction occurs with increased numbers of white blood cells entering the joint space. The white blood cells, themselves, release various chemical mediators that create further swelling and inflammation. Joint pain and many times fever are noted due to the inflammatory response. An obvious swelling in the joints may or may not be noted. If joint swelling is not present, the diagnosis may be quite difficult to establish.

There are no consistent signs of the disease and many of the signs are fairly general and may be seen with many other conditions. Animals with this disease generally feel ill and reluctant to move, which may be interpreted as lethargy rather than joint pain or stiffness. Sometimes the only noted clinical problem is a fever of unknown origin, and a very involved work up might be needed before a diagnosis can be established.

Animals with polyarthritis often experience shifting leg lameness or multiple limb involvement, again causing potential confusion. Additionally, the signs of polyarthritis may be acute (happening very quickly) or chronic (long standing). Oftentimes, animals seem to improve for a short time on their own, but usually their clinical signs return or become even worse. It is not uncommon for an animal that has been intermittently ill for months return to the hospital with polyarthritis.

If polyarthritis is suspected, it is important to establish the diagnosis of idiopathic immune-mediated disease. Since there is no specific diagnostic test that will confirm the idiopathic disease the diagnosis must be based on exclusion of other potential causes of polyarthritis.

Many other diseases that stimulate an inflammatory reaction can actually cause a similar immune response in the joints. The diagnosis of idiopathic immune-mediated disease is only made after these other conditions are ruled out. Diseases that can cause similar symptoms as immune-mediated polyarthritis include:

In-depth Information on Diagnosis

The diagnosis of immune-mediated polyarthritis is made in two parts. First, your veterinarian must establish a diagnosis of polyarthritis, which is often difficult. Once the polyarthritis is diagnosed, a cause needs to be determined. Since the diagnosis of immune-mediated polyarthritis is based on the exclusion of other causes, a significant work-up is usually required. Diagnostic tests include:

In-depth Information on Therapy

Generally, prednisone and Imuran are the most effective drugs used to treat the disease. In refractory cases, the following drugs may be of benefit:

Follow-up Care for Dogs with Immune-mediated Polyarthritis

Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not improve rapidly. Administer all medications as directed. Alert your veterinarian if you are experiencing problems treating your dog.

Even after your dog has gone into remission, careful observation is required. The signs of polyarthritis may recur even while on medication. Early recognition improves the chances of a second remission. This is especially important as immunosuppressive drugs are decreased.

Routine follow-up veterinary examinations are important while your dog is being treated. Subtle changes in joint size, shape or conformation may be noted.

Monthly blood tests are required (CBC and platelet counts) if your pet is receiving Imuran. The tests may be required more frequently if receiving Cytoxan.

If your dog is experiencing unusual behavior, it may be a side effect from the prednisone. The most common side effects include: increased thirst, urination and appetite; panting; lethargy; weakness; and muscle atrophy. Depending on the severity of these signs, the dosage may need to be adjusted and/or additional immunosuppressive drugs started.