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Systemic Lupus Erythematosus (SLE) in Cats

Autoimmune diseases are the result of an immune system that has become hyper-defensive, attacking the cells, tissues, and organs of its own body as if they are diseases that need to be destroyed. Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease that is characterized by the formation of antibodies against a wide array of self-antigens (antibody-generating substances) and circulating immune complexes.

High levels of circulating antigen-antibody complexes (type III hypersensitivity) are formed and deposited in the glomerular basement membrane (the filtration portion of the kidney), the synovial membrane (the soft tissue that lines the surface space within joints such as the wrist, knee, etc.), and in the skin, blood vessels, and other sites in the body. Antibodies that are directed toward self-antigens that reside on and within cells, such as erythrocytes, leukocytes, and platelets (three kinds of blood cells with type II hypersensitivity), may also be produced. To a lesser degree, type IV hypersensitivity may also be involved when cell-mediated immunity is directed against a self-antigen.

SLE is rare, but is believed to be underdiagnosed. Some of the breeds that appear to have a predilection for SLE include Persian, Siamese, and Himalayan cat breeds. The mean age is six years, but it can occur at any age. Gender does not play a role.

Symptoms and Types

Clinical symptoms depend on the localization of the immune complexes, along with the specificity of the autoantibodies. However, genetic, environmental, pharmacologic, and infectious factors may play a role in the appearance of clinical signs such as letahrgy, loss of appetite (anorexia), and fever, which is especially seen in the acute phase. Other signs include:

Musculoskeletal

• Deposition of immune complexes in the synovial membranes (the soft tissue lining the surfaces within the joints)
• Swollen and/or painful joints - major presenting sign in most patients
• Shifting-leg lameness
• Muscle pain or wasting

Skin/exocrine

• Deposition of immune complexes in the skin
• Skin lesions
• Symmetric or focal skin lesions - redness, scaling, ulcers, depigmentation, and/or hair loss
• Ulceration of mucocutaneous junctions and oral mucosa may develop - a region of skin comprising both mucosa and cutaneous skin; these mostly occur near the orifices of the body at which the external skin stops and the mucosa that covers the inside of the body starts (e.g., mouth, anus, nostrils)

Renal/urologic

• Deposition of immune complexes in the kidney
• Hepatosplenomegaly - enlargement of the kidney and the liver

Blood/lymph/immune system

• Autoantibodies against erythrocytes, leukocytes, or platelets (red and white blood cells)
• Lymphadenopathy - swollen lymph nodes
• Other organ systems may be affected if there is deposition of immune complexes or antibodies, or when T cell-mediated cells (lymphocytes) attack

Causes

The definitive causes for SLE are unidentified, but exposure to ultraviolet light may exacerbate the disease.

Diagnosis

A complete blood profile will need to be conducted, including a chemical blood profile, a complete blood count, and a urinalysis. You will need to give a thorough history of your cat's health and onset of symptoms, and whether the symptoms have occurred in succeeding order, or all at once. Pain in the joints, kidney inflammation, skin lesions, breakdown of red blood cells, low platelet count, and general body weakness are all signs that will alert your doctor to the likelihood of lupus.