Pigmentary Abnormalities in Animals

Many associations between skin and coat color and developmental anomalies have been recorded in domestic animals. Some of the associations with hypotrichosis are discussed under hereditary alopecia.

Albinism appears to be rare in domestic animals. True albinism is always associated with pink or pale irises and with visual defects and increased risk of solar radiation–induced skin neoplasms. It has been noted in Icelandic sheep and in Guernsey, Austrian Murboden, Shorthorn, Brown Swiss, and Charolais cattle. Albinism must be differentiated from extreme white spotting or piebaldism and dominant white. Some animals with extreme piebaldism or dominant white have associated neurological anomalies or deafness, or suffer death in utero.

Lethal white foal syndrome results from breeding two overo Paints. In dogs and cats, dominant white or extreme piebaldism can be associated with unilateral or bilateral deafness and sometimes with blue irides or iris heterochromia. White cats with bilateral blue eyes have a 75% chance of deafness. In dogs, deafness can also be associated with merle hair coats in Dalmatians, Sealyham Terriers, harlequin Great Danes, Collies, and white Bull Terriers. Cyclic neutropenia may be found in gray or pale merle Collies. In Rhodesian Ridgebacks, pale coat color is associated with cerebellar degeneration.

In Chédiak-Higashi syndrome of cats and cattle (Herefords, Japanese Black, Brangus), coat color dilution (blue smoke in cats) is associated with neutrophil and platelet abnormalities and shortened lifespan. This syndrome is inherited as an autosomal recessive trait. Male tricolor cats (calico and tortoiseshell) are sterile because the gene for orange is X-linked and recessive, and males have the abnormal XXY genotype.

Pigmentary abnormalities may be acquired, and some of these may be hereditary or familial, as in vitiligo. Some cases of vitiligo may be immune mediated. As a familial disease, vitiligo is best recognized in Arabian horses (Arabian fading syndrome, pinky syndrome); it may also be familial in cattle (Holstein-Friesian), Siamese cats, and some dog breeds (Belgian Tervuren, Rottweiler). Affected animals develop somewhat symmetrical macular depigmentation of the skin that occasionally also affects the hair coat and claws or hooves.

Vitiligo, horse

Image

Courtesy of Dr. Karen A. Moriello.

Onset of vitiligo is usually in young adulthood. Most lesions are on the face, especially on the muzzle or nasal planum or periocular (see image of horse with vitiligo). Depigmentation can wax and wane. Complete remission can occur but is rare. There is no accompanying systemic or cutaneous pathology. No treatment is available; treatments used in humans with vitiligo are unlikely to provide noteworthy cosmetic results in animals.

Lentigo in orange and orange-faced male cats is marked by the development of pigmented macules with no other clinical signs (see images of cats with lentigo). Lesions are first noted on the lips and eyelids at < 1 year old. Other sites include the nasal planum and gingiva. Lentigines are not precancerous and have no medical consequence.

Lentigo, cats

Image

Courtesy of Dr. Karen A. Moriello.

Acquired aurotrichia of Miniature Schnauzers is a familial syndrome beginning in young adulthood in which hair along the dorsal midline changes to golden from the normal black or gray of this breed. This change may be associated with thinning of the hair coat but no other cutaneous or systemic clinical signs. In most dogs, coat color reverts to normal within 1–2 years.