Erosive, Immune-Mediated Polyarthritis in Dogs
Erosive, immune-mediated polyarthritis is an immune-mediated inflammatory disease of the joints, in which the cartilage of the dog's joint (articular cartilage) is eroded away. In this disease, cell-mediated immunity is thought to attack articular cartilage. The suspected causes for this are T lymphocyte effector cells that carry out the attack response, and an abnormal antigenic response to the host antibody. That is, an immune response to a substance that stimulates production of antibodies, an antigen, which acts as a “trigger”. In effect, the body is fighting against itself.
Leukocyte cells (white blood cells), leukocyte enzymes (catalyzing reactions), cell-mediated immunity, immune complexes (an antibody bound to its triggering antigen), and autoallergic reactions are all directed against cartilage components. This leads to an inflammatory response by the tissue surrounding the cartilage, and complement protein activation in response to the immunity displaying cells.
Destructive enzymes, which are released from inflammatory cells, damage the articular cartilage, synoviocytes (cells which produce a lubricating fluid, called synovia, for the joints), and chondrocytes (cartilage cells), leading to erosive changes in the joints.
The disease described in this medical article can affect both dogs and cats. If you would like to learn more about how it affects cats, please visit this page in the PetMD health library.
Symptoms for dogs are often cyclic, coming and going at random intervals. These symptoms include:
- Stiffness in walk
- Decreased range of motion
- Cracking sounds from the joints
- Joint swelling and pain in one or more joints
- Joint instability, subluxation (partial dislocation of the joint), and luxation (complete dislocation of the joint)
The typical onset of immune-mediated erosive polyarthritis in dogs is from eight months to eight years of age. Young Greyhounds, between the ages of 3-30 months, are most susceptible to erosive polyarthritis of Greyhounds (EPG), a specific type of this disease. There is also idiopathic erosive polyarthritis (IEP), which can occur in any breed and is of unknown cause.
The suspected causes for this form of joint cartillage erosion are T lymphocyte effector cells that carry out the attack response, and an abnormal antigenic response to the host antibody. That is, an immune response to a substance that stimulates production of antibodies, an antigen, which acts as a “trigger.” In cases of IEP, the cause remains unknown.
You will need to give your veterinarian a thorough history of your dog's health leading up to the onset of symptoms. Your veterinarian will perform a thorough physical exam on your dog, taking note of signs of pain, decreased range of motion, and any lameness.
A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, a urinalysis, and an electrolyte panel. Joint fluid aspirate will be taken for lab analysis, and submitted for bacterial culture and sensitivity. A biopsy (tissue sample) of synovial tissue will also help to make a definitive diagnosis.
X-ray images can also be used as a diagnostic tool. If an erosive, immune-mediated polyarthritis condition is present, it will be visible on the radiograph image.
Physical therapy, including range-of-motion exercises, massage, and swimming can help treat severe disease. Bandages and/or splints may be placed around the joint to prevent further degradation of the cartilage, especially in dogs that are experiencing difficulty walking. Weight loss also helps decrease pressure on the joints if the dog is overweight.
Surgery for this condition is generally not recommended. However, total hip replacements, and femoral head ostectomy (surgical removal of part of the thigh bone) may be considered.
Arthrodesis of the carpus (wrist) is generally quite successful for treating joint pain and instability. Arthrodesis of the shoulder, elbow, stifle (knee), or hock (ankle), meanwhile, is not as reliable at yielding positive results.
Living and Management
Your veterinarian will schedule frequent follow-up appointments to examine your dog's progress. If your dog’s condition continues to worsen, you must contact your veterinarian immediately for care.
Removal of the bone through surgical means
A type of leukocyte in the body
A record of body structures using an x-ray
The displacement of the bone from its joint
An in-depth examination of the properties of urine; used to determine the presence or absence of illness
The dislocation of a bone from the joint
The term for the joint between the femur and tibia (knee cap)
Any type of pain or tenderness or lack of soundness in the feet or legs of animals
a) inhaling b) getting out fluid or gas by the act of sucking.
Any substance or item that the body of an animal would regard as strange or unwanted; a foreign disease or virus in the body (toxin, etc.)
The process of removing tissue to examine it, usually for medical reasons.
Loss of epithelium to the basement membrane
A protein in the body that is designed to fight disease; antibodies are brought on by the presence of certain antigens in the system.
Relating to a disease of unknown origin, which may or may not have arisen spontaneously
White blood cells that are known for destroying disease and help to keep foreign substances out of the blood