Systemic lupus erythematosus in a filly.

This study presents the case of a 2-year-old horse diagnosed with systemic lupus erythematosus (SLE), discussing the observed symptoms, lab findings, treatment attempt, and necropsy outcomes, to remind veterinarians that SLE should be considered when diagnosing immune-related skin problems in horses.

Details of the Clinical Case

• The horse studied was a 2-year-old filly of the Standardbred breed. She showed various symptoms that pointed towards an autoimmune disorder, more specifically SLE.
• The symptoms included weight loss, symmetrical hair loss (alopecia) on both sides of her body, excessive sebum production (seborrhea), mouth ulcers, and an inflammation of the lymph nodes (lymphadenopathy).

Laboratory Findings

• The filly’s abnormal laboratory results included a positive Coombs test, indicating the presence of autoimmune hemolytic anemia – a condition where the immune system attacks and destroys its own red blood cells.
• The antinuclear antibody (ANA) test was also positive, which often signifies the presence of an autoimmune disease. The ANA test detects antibodies that are targeted against the cell’s own nucleus.

Biopsy and Histologic Evaluations

• Multiple skin biopsies were examined under a microscope, shedding light on the skin changes associated with SLE. The biopsies showed interface dermatitis (inflammation of the skin) with linear deposits of antibodies (IgG) exactly at the junction between the epidermis and dermis, and around hair follicles, illustrating an abnormal immune reaction to the horse’s own tissues.

Treatment and Necropsy Findings

• Attempt to treat with a type of steroid, glucocorticoids, failed to provide any improvement in the filly’s condition.
• Due to the filly’s deteriorating condition, the decision was made to euthanize her. The subsequent necropsy revealed that damage had occurred in other tissues as well – the kidney had membrane inflammation with scarring (membranous glomerulonephritis), and severe inflammation with fibrous tissue deposition was seen in the joint synovium (fibrous synovitis).

Conclusion

• Based on these facts, the research suggests that SLE, while relatively rare, should be included in differential diagnosis when dealing with skin diseases seemingly caused by an immune response in horses.
• The definitive diagnosis of SLE is based on recognizing the presence of disease in multiple organs or systems, alongside confirmation through microscopic examination of tissues and detection of misdirected immune responses.