• Systemic lupus erythematosus (SLE) is a chronic, immune-mediated disorder in which a dog’s immune system targets its own tissues. The immune system produces autoantibodies against various cellular components (antigens) present in multiple organs, leading to widespread inflammation and organ damage. The disease can affect virtually any organ system, with signs ranging from dermatologic to renal to neurologic involvement.

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Etiology

• Pathogenesis: SLE is a multifactorial disease, influenced by genetic predisposition, environmental triggers, and immune dysregulation. Genetic factors predispose certain breeds to SLE, although the precise triggers for disease onset remain unclear.

  • Genetic Predisposition: Medium to large breed dogs are overrepresented. Notable predisposed breeds include:

    • Afghan Hound

    • Beagle

    • Collie

    • German Shepherd

    • Irish Setter

    • Old English Sheepdog

    • Poodle

    • Shetland Sheepdog

  • Age: The mean age of onset is around 5 years, though SLE can occur in dogs as young as 6 months.

  • Sex: Male dogs may have a slightly higher incidence than females in some studies.

  • Environmental Factors: UV exposure, certain viral infections, or chemicals may act as potential triggers, although evidence is inconclusive.

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Clinical Signs

• SLE can have a relapsing-remitting course, with symptoms that may wax and wane over time. Clinical signs vary depending on which organ systems are primarily affected. Signs can range from acute to chronic.

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• Key Clinical Features:

  • Lethargy and decreased activity: Due to generalized inflammation and immune activation.

  • Shifting leg lameness: Often occurs due to immune-mediated synovitis in the joints, leading to polyarthritis. The lameness may shift from one limb to another.

  • Dermatologic signs:

    • Erythema (redness), thinning of the skin, and alopecia.

    • Ulceration and depigmentation at the mucocutaneous junctions (e.g., lips, nasal planum).

    • Chronic photosensitivity in affected dogs.

  • Fever: Commonly reported, associated with immune system activation.

  • Enlarged lymph nodes (lymphadenopathy) and splenomegaly or hepatomegaly.

  • Renal involvement: Proteinuria (often seen on urinalysis), which may progress to chronic kidney disease.

  • Muscle pain, atrophy, and possible neurologic signs: In severe cases, dogs may develop seizures or behavioral changes due to central nervous system involvement.

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Diagnosis of SLE

• The diagnosis of SLE in dogs is clinical and requires laboratory confirmation. The presence of autoantibodies along with suggestive clinical signs helps confirm the diagnosis. Diagnostic challenges include its overlap with other autoimmune diseases and systemic conditions.

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• Diagnostic Approach:

  • Blood Work:

    • Anemia, leukopenia, and thrombocytopenia can occur due to immune-mediated destruction of blood cells.

    • Elevated liver enzymes (ALT, ALP) and kidney dysfunction (elevated creatinine, BUN) may be seen if these organs are involved.

    • Antinuclear antibody (ANA) test: A positive ANA test is suggestive of autoimmune disease but not specific to SLE. A titer > 1:160 is typically considered supportive.

    • Anti-dsDNA antibodies: Highly specific for SLE, although not always present early in the disease course.

  • Urinalysis: The presence of proteinuria (increased urine protein-to-creatinine ratio) is an important indicator of renal involvement, often seen in lupus nephritis.

  • Biopsy of Affected Tissues: Skin and kidney biopsies may reveal characteristic immune complexes, which can confirm the diagnosis of SLE.

  • Imaging: Radiographs and ultrasound are mainly used to assess for organomegaly (liver, spleen) and detect any underlying renal or hepatic abnormalities.

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Treatment of SLE

• The treatment of SLE is aimed at immune modulation and supportive care. There is no cure, but many dogs can have good quality of life with appropriate management. Immunosuppressive therapy is the mainstay of treatment, often combined with supportive care to address specific organ involvement.

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• First-line Treatment:

  • Corticosteroids (e.g., prednisone): These are typically the initial therapy for controlling inflammation and immune system activity. They help with dermatologic, arthritic, and fever-related symptoms.

  • Immunosuppressive Drugs: In more severe or refractory cases, additional immunosuppressive medications may be required:

    • Azathioprine

    • Mycophenolate mofetil

    • Cyclophosphamide (particularly in cases with severe nephritis)

  • Nonsteroidal anti-inflammatory drugs (NSAIDs): In cases of joint inflammation or mild pain, NSAIDs may be used alongside corticosteroids to minimize side effects from steroid therapy.

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• Supportive Care:

  • UV Protection: For dogs with photosensitivity, protective measures such as avoiding sun exposure or using sunscreen are essential to prevent skin lesions.

  • Dietary management: If there is renal involvement, a high-quality, renal-specific diet may be necessary to manage proteinuria and preserve kidney function.

  • Infections: Dogs with SLE are immunocompromised and may be at increased risk for secondary infections. Antibiotics and antifungal treatment may be required as part of supportive care.

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Long-term Management & Prognosis

• The prognosis for SLE varies significantly based on the severity of organ involvement and the response to treatment.

• Prognostic Factors:

  • Mild cases (primarily skin or joint involvement) tend to have a more favorable prognosis, with many dogs living for several years with appropriate immunosuppressive therapy.

  • Renal involvement (particularly lupus nephritis) is associated with poorer outcomes, especially if kidney function declines despite treatment.

  • Neurologic or hematologic involvement may also signal a more grave prognosis.

• Complications:

  • Side effects of immunosuppressive therapy: Long-term corticosteroid use can lead to secondary infections, gastrointestinal ulcers, and hyperadrenocorticism (Cushing’s disease).

  • Chronic kidney disease: Dogs with significant renal involvement may develop progressive renal failure despite immunosuppressive therapy.

  • Relapse of disease: SLE often has a relapsing-remitting course, requiring ongoing management and monitoring.

• Long-term Care:

  • Regular monitoring of kidney function, blood pressure, and serum protein levels is essential, especially in dogs with renal involvement.

  • Frequent re-evaluation of immunosuppressive drug doses to balance efficacy with minimizing side effects.

  • Vaccination and preventative care may need to be adjusted to account for the immunocompromised status of the patient.