Vitiligo in a Quarter Horse Filly: Clinicopathologic, Ultrastructural, and Nutritional Study

Vitiligo is an autoimmune disorder characterized clinically by depigmentation of the skin—both epidermis and hairs—caused by destruction of melanocytes. Vitiliginous skin shows a T-lymphocyte inflammatory infiltrate, proliferation of Langerhans cells, epidermal vacuoles, and degenerative changes in the cutaneous nerve fibrils. Increased autoantibodies against melanin, tyrosinase, and various tissues are frequently present in vitiligo patients. Vitiligo is often associated with systemic abnormalities or nutritional deficiencies. A 2-year-old Quarter Horse filly developed facial vitiligo with depigmented areas that was strikingly similar to human vitiligo. Several innocuous small biopsies provided cutaneous specimens that were processed for light and electron microscopic studies. Many of the clinical and microscopic changes observed in human vitiligo were present in this equine patient. Marginal anemia was detected. Strengthening of the filly's nutritional and feeding conditions led to rapid and complete repigmentation. Equine practitioners as well as horse owners should be aware that vitiligo may not be simply a cosmetic problem; thus, a complete evaluation of horses affected by this condition should be performed.