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IMPA: Immune-Mediated Polyarthritis in Dogs (Non-erosive)


There are many reasons that your dog might develop arthritis. Today we will talk about one possible cause -- immune-mediated polyarthritis (IMPA).

What is immune-mediated polyarthritis?
In the case of this disorder, "poly” refers to the fact that this condition affects more than one joint and “immune-mediated” specifies that the body’s own immune response actually causes the problem. IMPA comes in two forms: erosive (destructive) and non-erosive, so we will further narrow the scope of this discussion to non-erosive IMPA—since that is the most common cause of polyarthritis in dogs.

What causes immune-mediated polyarthritis?
I mentioned earlier that with IMPA your dog’s own immune system is responsible for the inflammation. As you probably know, your immune system responds to infection, but IMPA doesn’t mean that there is an infection inside your dog’s joints. In fact, just the opposite is true. IMPA has no identifiable infectious component in the joints themselves. That said, something happens somewhere in the body that stimulates an antibody response. Those antibodies bind to antigens, and those complexes accumulate in the joint fluid; in turn they set off a sequence of cellular and chemical reactions that result in an inflammatory response.

The list of possible causes is extensive. Certainly infections (viral, bacterial, fungal, etc) elsewhere in the body can be responsible. It can also be a response to:

  • Cancers
  • Physical traumas
  • Drugs
  • Vaccine administration

All together these causes can be categorized as reactive IMPA.

There are also breed associated IMPA causes in some dogs (i.e., Akitas, Shar peis, and Bernese Mountain Dogs). Alternatively, IMPA can be a component of an uncommon, immune-disorder called systemic lupus erythematosus. However, if none of these other conditions, or underlying causes, are responsible for IMPA, then it’s classified as idiopathic (we don’t know the cause).

What are the symptoms of immune-mediated polyarthritis?
Obviously, if your dog develops IMPA secondary to another disease process, then the symptoms would be highly variable; but dogs with IMPA can present with:

  • Fever
  • Inappetance/weight loss
  • Lethargy
  • Reluctance to move
  • Stiffness
  • Lameness
  • Swollen joints/joint pain (I have seen dogs that simply would not move at all, dogs that nearly did hand stands coming down stairs and many dogs with the classic "walking on tippy toes/eggshells" type of gait.)

It’s important to realize that not all dogs will present with all, or even any, of these symptoms so diagnosis can be difficult.

How is immune-mediated polyarthritis diagnosed?
The definitive test to confirm IMPA is a joint tap and analysis of the fluid sample obtained. You may know someone who receives injections into their joints for chronic arthritis. Removing a bit of joint fluid is pretty much the same process in reverse. The joint tap does need to be performed carefully (so as not to introduce infection where it did not exist) and may require light sedation (especially since by definition this is a POLYarthritis so multiple joints will need to be aspirated). Joint taps are generally well-tolerated, minimally invasive tests.

Since we discussed the fact that this condition can occur secondary to other diseases or disorders, it is important to perform other diagnostic tests including:

  • Blood work
  • Urinalysis
  • Urine cultures
  • Radiographs
  • Ultrasounds

How is immune-mediated polyarthritis treated?
Because IMPA is the result of an immune response, treatment protocols center on the use of immunosuppressive drugs. These medications can require relatively high doses for initial effect and treatment may need to be continued for relatively long periods of time. Once again, it’s important for your veterinarian to adequately rule out other causes of arthritis (especially infectious ones) and other underlying disorders that require separate treatments. In addition, careful monitoring for adverse effects associated with the immunosuppressive treatment itself is necessary—as are repeat joint taps.

If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.


Future treatments?

Treatments for various types of arthritis might one day include a dose of beneficial microbes. Carl Warden, for instance, reported in 1909 that giving patients milk containing live Streptococcus lacticus and Bacillus bulgaricus cultures helped symptoms of inflammatory arthritis in some patients 18 .

Today, scientists still aren’t sure whether probiotics —ingestible cultures of live bacteria—are beneficial in arthritis treatment or not 19 . The results from various studies stemming from Warden’s initial observations have been inconsistent. This could be because the supplements are lacking the right strains of bacteria or because it depends on the person—additional studies are needed and most certainly underway.

While research has been done in humans and animal models of disease, stay tuned for what scientists learn in pets. Future research could find similar links among gut bacteria and various types of arthritis, which would be a step toward making our beloved pets more comfortable.


How Likely is it That my Dog Will Develop Arthritis?

Unfortunately, arthritis in dogs is very common. According to the Arthritis Foundation, more than 20% of the roughly 80 million pet dogs in the United States are diagnosed with some form of arthritis. For dogs older than seven years, the likelihood of suffering from arthritis increases to over 65%. In other words, more than half of all senior dogs have arthritis.⁶

Causes leading to canine arthritis are diverse. While some of the causes are specific to a certain type of arthritis, others are contributors to arthritis in general.

Possible Contributing Factors and Causes of Arthritis in Dogs

  • Hereditary and genetic predisposition play an important role. This can be related to the pedigree of a specific dog, or to an entire breed. Dobermans, German Shepherds, and Labradors are for example known to be predisposed for septic arthritis.
  • Joint instabilities like hip or knee dysplasia and patellar luxation, can cause excess wear of the cartilage and over time lead to arthritis.
  • Autoimmune disorders, such as systemic lupus erythematosus, can also cause inflammation of one or more joints, ultimately leading to lameness and arthritis.
  • A compromised immune system because of cancer, vaccine administration, etc. may be unable to appropriately fight infections. Infections affecting the joints of your canine may cause permanent damage, leading to arthritis.
  • Joint damage and arthritis are twice as likely to occur in dogs that are diagnosed with diabetes.
  • Joint infections and injuries to ligaments or cartilage are also possible causes of arthritis.
  • Larger dogs are more likely to develop arthritis than smaller dogs.
  • Overweight or obese dogs are in general tending to develop arthritis more often than their fit counterparts.
  • Typical canine nutrition in the United States is high in omega-6 fatty acids and deficient in omega-3 fatty acids. Additionally, grains and corn are typical fillers used in dog food. This dietary composition supports inflammation and can therefore contribute to arthritis.
  • Rapid growth as a puppy, typically caused by over-nutrition, may lead to skeletal disorders. These can over the lifetime of your canine companion result in joint damage and arthritis. Especially large and giant breeds are at risk.
  • Dog sports and excessive jumping might in extreme cases result over time in abnormal wear of cartilage, leading to chronic joint pain and arthritis.
  • Additionally, the likelihood of a pet developing arthritis grows with age.

Should your dog fall into any of the above categories, please pay special attention to them for showing possible signs of arthritis.


Immune-mediated Arthritis in Dogs and Cats

, MS, DVM, DACVS, Veterinary Surgical Specialists, Spokane, WA

Inflammatory polyarthritis secondary to deposition of immune complexes can produce erosive (destruction of articular cartilage and subchondral bone) or nonerosive (periarticular inflammation) forms of joint diseases. Rheumatoid arthritis, Greyhound polyarthritis, and feline progressive polyarthritis are examples of erosive arthritides. Systemic lupus erythematosus is the most common form of nonerosive arthritis.

Clinical signs are lameness, multiple joint pain, joint swelling, fever, malaise, and anorexia. Clinical signs commonly wax and wane.

Diagnosis is aided by radiography, biopsy, arthrocentesis, and serologic testing. Radiography reveals periarticular swelling, effusion, and joint collapse plus subchondral bone destruction in erosive conditions. Joint fluid analysis will reveal elevated cell counts exceeding 3,000/mcL, composed primarily of normal polymorphonuclear cells. Biopsy of synovial tissue reveals mild to severe inflammation and cellular infiltrates. Serologic testing is performed for rheumatoid factor and antinuclear antibodies.

Treatment involves anti-inflammatory medications (eg, corticosteroids) and chemotherapeutic agents (eg, cyclophosphamide , azathioprine , or methotrexate ). Prognosis is guarded because of relapses and inability to determine the inciting cause of the autoimmune reactions.


IMPA or Immune-Mediated Polyarthritis in Dogs

Immune-Mediated Polyarthritis or IMPA is an inflammatory disease of the movable joints that affects dogs. Immune-mediated means that the disease is brought about by the dog’s own immune system, and polyarthritis in dogs refers to inflammation in more than just one joint.

With an overactive immune system sometimes the body produces an over abundance of white blood cells and attacks itself. This is similar to the achy feeling when we have the flu. The immune system is revved up to fight off infection but also affects normally healthy joints.

This is precisely what happens in IMPA. White blood cells function improperly and attack healthy joints leading to pain, inflammation, and difficulty walking.

IMPA Overview

There are two types of IMPA that are brought on by various factors. Veterinarians categorize IMPA as either Erosive or Non-Erosive. Erosive IMPA is less common and affects only one percent of dogs with this disease. It is similar to rheumatoid arthritis in humans. Erosive IMPA is rare in dogs and it destructs cartilage as well as bones.

Non-Erosive IMPA is the more common form of the disease, and is not joint destructive. Veterinarians may determine the type by performing X-rays, blood tests, urine cultures and sometimes joint taps. Because it is an auto-immune disease the vet will do tests to ensure there is not an underlying cause such as cancer or infection. If the tests do not reveal evidence of an underlying cause, then the condition is termed “autoimmune” polyarthritis.

The reason for this misdirected attack is not completely clear. Some breeds are more susceptible. It it thought IMPA can develop due to antibiotic use and even as a side effect from certain vaccines. Age, diet, obesity and stress may also play roles in the disease development.

Joint disease is common in all ages and breeds of dogs – in fact one in five dogs are believed to have it. While IMPA can affect all sizes of dogs, it is more common in larger breeds. The breeds more prone to this disease are Akitas, Sharpeis, German Shepards and Burmese Mountain Dogs.

The National Institutes of Health has an in-depth published study of IMPA where 83 cases were studied over an 11 year period.

IMPA causes achy and sore joints due to inflammation. Some signs your pet may have IMPA are a reluctance to walk, difficulty handling stairs, whimpering when walking, or appearance to “walk on eggshells.” These symptoms may also include lack of appetite, low-grade fever, a reluctance to play, and mild joint swelling.

The most common symptom of IMPA in dogs is joint pain. If your pet is experiencing any type of joint pain, a supplement like Flexpet can be very beneficial. Flexpet is an anti-inflammatory and a pain reliever. It helps to alleviate the discomfort caused by painful joints so your pets can go back to living a normal, active life.

If you suspect that your dog may have IMPA or they are experiencing these types of symptoms it is important to seek veterinary help to determine the cause of your dog’s pain.

As with any auto-immune disease, the first step in avoiding IMPA is prevention. There are a number of different precautions you can take to help protect your pet from this debilitating disease. Maintaining a healthy weight and diet are very important. Also, you may want to consider a supplement, especially as your pet ages. If your dog has been diagnosed with IMPA your vet may prescribe medication.

A common medication prescribed for IMPA is a steroid such as Prednisone or Prednisolone. This strong medication is prescribed to temporarily relieve pain due to its anti-inflammatory properties. This medication can only be used temporarily because prolonged use may damage tissue such as stomach lining, and it also has many other side effects. These include vomiting, diarrhea, aggression or behavioral changes, and lethargy.

Nonsteroidal Anti-Inflammatory Drugs – NSAIDs

Another option is to use a Nonsteroidal anti-inflammatory drug. NSAIDs are medications that relieve or reduce pain. The most popular examples of this group of drugs are TRAMADOL, RIMADYL (carprofen), METACAM (meloxicam), NOVOCOX (carprofen), GALLIPRANT or PREVICOX (firocoxib). Again, NSAIDs provide temporary relief and are not without long term use side effects. The side effects of NSAIDs are mainly seen in the digestive tract, kidneys, and liver.

Supplements for IMPA and Joint Pain

Using prescribed medications is a balancing act where you have to weigh the benefits against the risks. Considering an all-natural joint pain relief supplement that has no known side-effects may be a route you want to take in relieving your pet’s pain and inflammation.

Flexpet is an excellent solution to help alleviate the symptoms of IMPA and keep your dog pain free. Flexpet offers an all-natural alternative to other medications that works hard to get to the root of the problem.

In addition to helping relieve pain, Flexpet helps your dog in other ways. Its active ingredients work to lubricate your dog’s joints, as well as help rebuild joints and cartilage. There are also natural enzyme ingredients in Flexpet that make sure your dog is digesting the supplement properly, and that the healing aspects are being properly retained.

FlexPet’s patented ingredient CM8, also known as cetyl myristoleate, is a natural anti-inflammatory that lubricates and reduces swelling in the joints. Flexpet also contains:

GLUCOSAMINE SULFATE POTASSIUM: A naturally occurring chemical found in mammals that reduces stiffness, joint swelling and osteoarthritis related pain. Glucosamine plays a key role in cartilage construction and the incorporation of sulfur into cartilage.

MSM (METHYLSULFONYLMETHANE): MSM is a sulfur compound that occurs naturally in plants and animals. Sulfur is needed by the body to form connective tissue. The MSM in Flexpet products has been specially formulated to increase the absorption rate of sulfur.

HYDROLYZED COLLAGEN TYPE II: This is an ingredient found in cartilage, the connective tissue that cushions the joints. Collagen is made of amino acids (the building blocks of protein) and it is used in an effort to protect and rebuild joint cartilage.

BROMELAIN: An enzyme found naturally in pineapple is used to reduce swelling especially after surgery or injury. It has also been shown to reduce sinus inflammation.

ENZYME BLEND: Digestion is dependent on enzymes produced naturally by the body. Larger molecules like Cetyl Myristoleate require more effort for the body to digest and absorb. Our natural enzyme blend is a complex proteinaceous substance used to induce and accelerate reactions necessary for metabolism.

Giving your pet the recommended dose of Flexpet to treat IMPA symptoms can help keep your pet healthy, happy, pain-free, and return to a more active lifestyle.


Watch the video: Hip dysplasia in Boxer Puppy. (May 2021).