SYSTEMIC LUPUS ERYTHEMATOSUS

About the Diagnosis

Systemic lupus erythematosus (SLE, "lupus") is an autoimmune disease that can affect multiple body systems. Normally, the immune system attacks foreign substances or organisms that invade the body. Autoimmune diseases occur when the immune system mistakenly attacks parts of the body. In SLE, multiple body tissues are targeted by the immune system. Susceptibility to developing SLE appears to be genetically determined, but environmental factors seem to trigger the onset of the disease. Some drugs can trigger a disease similar to SLE. The role of environmental factors in the development of SLE remains under investigation.

Symptoms are extremely variable, and SLE is sometimes referred to as "the great impostor" because of the wide spectrum of symptoms it may cause. Symptoms vary depending upon the body systems affected. The joints, kidneys, and skin are often involved. Other systems, including the muscles, nervous system, heart, and lungs can also be affected. Affected pets may have a chronic fever, stiff gait or limping (lameness), joint swelling, weakness, skin changes, ulcers in the mouth, increased drinking and urination, and behavioral changes.

Diagnosis: There is no single definitive test for SLE. Diagnosis depends upon the presence of several of the symptoms listed above plus a series of suggestive findings on laboratory tests. Routine blood tests may reveal anemia and changes in the white blood cell count. Kidney problems are often present as part of SLE, and traces of this may be detected on routine blood tests and urinalysis. Skin biopsies may support the diagnosis of autoimmune disease. A test to detect a type of antibody produced in SLE, the antinuclear antibody (ANA) titer, may give more evidence of the disease. However, both false positive and false negative results are possible. Weighing the combination of symptoms and laboratory tests results is involved in making a diagnosis of SLE.

Living with the Diagnosis

Pets with SLE will often respond to treatment and have symptoms that improve or disappear. They are also prone to having relapses of the disease, however, even after successful treatment of the initial episode. Laboratory testing should be repeated every few months to monitor for relapses and to assess the status of vital organs that could be affected by SLE.

Treatment

Treatment depends upon the severity of the disease in your pet. Lameness (limping) due to arthritis can be controlled by anti-inflammatory medications. Your veterinarian will prescribe a suitable medication. Cats cannot tolerate many of these drugs, so do not use over-the-counter or other anti-inflammatory drugs without the advice of your veterinarian. More severe signs require the administration of corticosteroids, such as prednisone.

Corticosteroids have many potential side effects, so their use should be monitored by your veterinarian. If your pet does not tolerate corticosteroid therapy or if the disease is severe, immunosuppressive therapy is indicated. This allows lower doses of corticosteroids and control of severe or persistent symptoms. Azathioprine is most often used in dogs; chlorambucil is frequently chosen for cats. Immunosuppressive therapy requires frequent monitoring by your veterinarian for possible side effects. After your pet's disease is controlled and the symptoms are reduced or resolved, the dose of the drugs used will be gradually tapered to the lowest effective level.

DOs

• Realize that no single test is conclusive for lupus and that the diagnosis requires several diagnostic tests for confirmation.

• Keep your pet from being exposed to sunlight since ultraviolet radiation may make the condition worse, especially with skin lesions.

• Give all medications exactly as instructed.

DON'Ts

• Don't stop medication or lower the dose without consulting your veterinarian.

When to Call Your Veterinarian

• If you notice any of the medication side effects listed under Signs to Watch For.

Signs to Watch For

• Corticosteroids can cause a variety of side effects including panting, increased appetite, increased drinking and urination, and temperament changes. These are to be expected. However, side effects that are more significant and warrant consultation with your veterinarian include loss of muscle mass around the head and face, decreased appetite, and sluggishness or inactivity (compared to normal).

• Side effects of immunosuppressive agents can result in vomiting, lack of appetite, inactivity, and infections.

Routine Follow-Up

• Frequent checkups are required at first to monitor the effectiveness of treatment and to screen for side effects of treatment as a precaution. Corticosteroid therapy and immunosuppressive drugs can potentially cause a variety of side effects. Routine blood tests and analysis of urine samples are necessary to look for problems such as bone marrow suppression, resulting in anemia and lowered resistance to infection. Immunosuppressive drugs such as azathioprine or chlorambucil may cause bone marrow suppression. Inapparent infections, such as urinary tract infections, may occur, so periodic testing is necessary to minimize the risk of more severe or generalized infections. After your pet's disease is under control, regular rechecks are helpful in early detection of disease flare-ups.