Nonerosive, Immune-Mediated Polyarthritis in Cats

Nonerosive immune-mediated polyarthritis is an immune-mediated inflammatory disease of the diarthroidal joints (movable joints: shoulder, knee, etc.), which occurs in multiple joints, and in which the cartilage of the joint (articular cartilage) is not eroded away. A type III hypersensitivity reaction, which causes antibodies to be bound to an antigen, in this case joint tissue, causes this condition.

These antibody-antigen complexes are called immune complexes, and they are deposited within the synovial membrane (where the fluid that lubricates the joints is held). There, the immune complexes trigger an abnormal immune response to the joint cartilage. What this means is that, in effect, the body is fighting itself. This leads to an inflammatory response, and complement protein activation by the tissue surrounding the cartilage, in response to the immunity displaying cells, leading to the clinical signs of arthritis.

Symptoms

• Stiffness in legs
• Lameness
• Decreased range of motion
• Cracking of the joints
• Joint swelling and pain in one or more joints
• Joint instability, subluxation (partial dislocation) and luxation (complete dislocation)
• Often cyclic, comes and goes
• Shifting leg lameness (in cats) - usually the stifle (knee), elbow, carpus (wrist), and tarsus (part of the ankle joint) are affected

Types

• Systemic lupus erythematosus: a noninfectious disease in which nuclear material from various cells becoming antigenic; autoantibodies (antinuclear antibodies) are formed to attack the body’s own joints
• Idiopathic polyarthritis: of unknown origin
• Polyarthritis associated with chronic disease: chronic infectious, neoplastic (uncontrolled growth of tissue), or enteropathic disease (intestinal disease)
• Polyarthritis-polymyositis syndrome: combination of arthritis in multiple joints, with weakness, pain, and swelling of the muscles
• Polymyositis syndrome: weakness, pain, and swelling of the muscles in the neck and legs
• Polyarthritis-meningitis syndrome: combination of arthritis in multiple joints with inflammation of the brain, with fever, pain, and stiff muscles
• Polyarthritis nodosa: arthritis in multiple joints with small nodular swellings
• Lymphocytic-plasmacytic synovitis: swelling of the synovial membrane of the joint (where the lubrication for the joint is produced) as the result of antibody attack on the tissue
• Proliferative form of feline chronic progressive polyarthritis (FCPP): rapid spreading of polyarthritis

Causes

• Idiopathic (unknown)
• Immunologic mechanism likely: abnormal immune response to the system
• May occur secondary to a hypersensitivity reaction to sulfas, cephalosporins, lincomycin, erythromycin, and penicillins, involving the deposition of drug antibody complexes in the blood vessels of the synovium (lining of the joint)
• The feline leukemia virus (FeLV, and feline syncytium-forming virus (FSFV) are linked to cats with Feline chronic progressive polyarthritis
• Chronic cases:
  • Antigenic stimulation along with concurrent meningitis (brain swelling)
  • Gastrointestinal disease
  • Neoplasia: uncontrolled growth of tissue
  • Urinary tract infection
  • Periodontitis: infection of the tissues that support the teeth
  • Bacterial endocarditis: bacterial infection of the heart lining
  • Heartworm disease
  • Pyometra: infection and accumulation of pus in the uterus
  • Chronic otitis media (infection of the middle ear) or external fungal infections
  • Chronic Actinomyces or Salmonella infections: bacterial infections, with fever, abscesses

Diagnosis

You will need to give your veterinarian a thorough history of your cat's health leading up to the onset of symptoms. Your veterinarian will perform a thorough physical exam on your cat, 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 a nonerosive, immune-mediated polyarthritis condition is present, it will be visible on the radiograph image.