Vitiligo is a hereditary skin disease which is not noticeable at birth and generally develops in animals less than 3 years of age. Affected dogs develop bleached splotches of skin that occasionally also affect the hair coat and claws. Most splotches are on the face, especially the bridge of the muzzle or around the eyes. Similar patches also appear on both the mucous membranes and perhaps in the retina. The hair that grows on areas affected by vitiligo sometimes turns white. Lesions surrounding the nares, eyes, anus, mouth and genitals have no inflammation or scaling. Affected areas may re-pigment, remain unchanged or wax and wane. Usually the full extent of the depigmentation occurs within 3 to 6 months of the onset of the disease. Although loss of pigment cells (melanocytes) from the skin is almost always the primary and initial symptom in vitiligo, other pigment cells in the body can be affected. Melanocytes are located in the inner ear and vitiligo-associated hearing problems have been reported in some patients. Damage can also occur to melanocytes within the eye, which is associated with abnormalities of the retinal pigment and uveitis.
A marked breed predisposition exists for the Belgian Tervuren. Other breeds at increased risk are the Rottweiler, Doberman Pinscher, German Shepherd Dog, German Shorthaired Pointer, Old English Sheepdog, and Dachshund. The disease occurs with varying amount of severity and no treatment is available. However, compounds derived from black pepper extract have shown potential to be effective in treating vitiligo.
Many possible causes of vitiligo have been proposed, including stress, infections, mutations, neurological factors, defects of skin pigment receptors, and impaired distribution of melanocytes. In addition, accumulation of toxic products of melanin synthesis, the breakdown of free radical defense, and the build-up of excessive quantities of hydrogen peroxide have all been suggested to result in the self-destruction of pigment cells. Vitiligo is a common manifestation of hypoparathyroidism Many studies have also associated vitiligo with autoimmune diseases.
A mottled loss of pigmentation can occur on all four paw pads. When vitiligo affects only the nose, the condition is sometimes referred to by dog breeders as "snow nose." Sometimes depigmentation only affects the bridge of the nose and the adjacent muzzle areas. This condition has also been termed "Dudley nose." "Dudley nose" and "snow nose" conditions have been reported in the Golden Retriever, yellow Labrador Retriever, Siberian Husky, Alaskan Malamute, and other northern breeds. A form of vitiligo involving the nose bridge area has been observed in dogs eating from rubber food dishes that contain benzyl hydroquinone. Apparently this chemical is absorbed through and inhibits melanin synthesis. The condition is reversible.4