Dogs can develop lupus (systemic lupus erythematosus, SLE), an immune-mediated disorder that affects multiple body systems. The cause is unknown, but genetic, environmental and, possibly, infectious processes may be involved. Either sex of dog may be affected in equal numbers. Although relatively rare in dogs, SLE occurs more frequently in dogs than in cats. Cats, unlike dogs, only rarely develop immune-mediated disorders.
In SLE, the affected dog's immune system produces antibodies against the dog's own tissues, reacting to them as if they were foreign invaders. This in turn stimulates an inflammatory reaction. The basic pathology of SLE revolves around the effects of this inflammation on the affected body systems, which produce the disease's clinical signs. SLE may affect the joints, skin, muscles, kidneys, blood and blood vessels, heart, and other organs.
Signs of SLE will vary among cases, and may occur acutely or slowly and off and on over weeks or months. Many affected dogs will have shifting leg lameness, a consequence of polyarthritis (multiply and symmetrically affected joints). The joints and muscles may also be swollen and tender to the touch. The skin is commonly involved. Ulcers, a red rash, dermatitis, crusts or scales, hair loss, and occasionally boils may appear. Protein spillage in the urine, a sign of kidney involvement, and hemolytic anemia, decreased red and white blood cell counts and platelet count may be discovered with laboratory tests. Other, minor, signs of SLE may include inflammation of the heart muscle (myocarditis) and linings of the heart and lungs (pericarditis and pleuritis, respectively). Affected dogs may have a fever, loss of appetite, seizures or a change in behavior.
Diagnosis of lupus is reached with a positive combination of clinical signs and laboratory diagnostic tests. SLE may have some signs in common with certain infectious diseases, neoplasms (new growths or tumors) and other conditions. Your veterinarian may order appropriate tests to rule out these other conditions. Radiographs (x-rays) of affected joints will allow differential diagnosis between lupus-associated joint disease and other forms of arthritis. A complete blood count (CBC) will reveal anemia and other blood cell disorders. A blood chemistry panel and urinalysis may demonstrate nonspecific changes consistent with SLE.
Several tests for SLE are available, including the antinuclear antibody (ANA) test and the lupus erythematosus (LE) cell preparation. However, test results are highly interpretative, and must be evaluated cautiously. Dogs with elevated levels of circulating lupus-associated antibodies (ANA titers) do not always have lupus; other conditions may result in elevated ANA titers as well. Additionally, some dogs with lupus will not have an elevated ANA titer. Unfortunately, there is no single, definitive test for SLE. Tissue biopsies may display changes characteristic of immune-mediated disease.
Treatment involves suppressing the immune system and the resultant tissue inflammation. Corticosteroids, such as prednisone, are the mainstay of treatment. Other immunosuppressive agents may be required to achieve a clinical remission; life-long treatment is expected. Organ system dysfunction resulting from SLE should be addressed as well. The prognosis is considered guarded. Progressive organ dysfunction and failure indicate a poor prognosis.
Veterinary internists are frequently consulted for diagnostics and treatment options of canine patients that may have systemic lupus erythematosus.
05/07/01
