Systemic Lupus Erythematosus in a Filly

Systemic lupus erythematosus (SLE) was diagnosed in a 2-year-old Standardbred filly, presenting with symptoms such as weight loss, bilateral symmetric alopecia, seborrhea, oral ulceration, and lymphadenopathy. Laboratory tests showed Coombs test-positive hemolytic anemia and a positive antinuclear antibody test. Skin biopsies revealed interface dermatitis with IgG deposition at the basement membrane zones. The filly did not respond to glucocorticoid treatment and was euthanized. Necropsy showed membranous glomerulonephritis and fibrous synovitis. The study suggested that SLE should be considered in the differential diagnosis of immune-mediated skin diseases in horses, with diagnosis relying on recognizing multisystemic disease and confirmatory histopathologic findings.