Pigmentary Skin Changes in Dogs
Changes in skin pigment can be alarming for pet parents, but when should a change in skin or hair color be a cause for concern? We break down causes for pigmentary skin changes and when it’s time see your veterinarian for a work up!
Causes of Hyperpigmentation
Hyperpigmentation (or darkening of the skin) can be provoked by a variety of causes. Location and appearance of the affected area may help differentiate the cause.
Skin that has previously been inflamed and may be affected by allergies or other primary skin conditions can develop a lacy texture, which presents as a brown or black darkening of the skin. The colored area will be flat and not crusted, and is thought to be a normal part of the skin healing after inflammation. This color may fade over time, but in some cases, it can persist.
Lentigo is a small, dark black, flat patch of skin. Pugs have their own inherited form of lentigo, known as lentiginosis profusa. Lentigo is considered a cosmetic change and doesn’t require treatment, since it doesn’t physically bother your pet. However, it can be hard to differentiate from early melanocytic neoplasia or viral (papilloma) plaques, so if you notice new dark spots on your dog, you should consult your veterinarian.
Pigmented Viral Plaques
Papilloma viruses can result in numerous skin lesions in dogs. One form, known as viral plaques, will create hyperpigmented, scaly-crusted, slightly-raised areas of skin. Viral plaques are most commonly seen in Pugs, Miniature Schnauzers, and Shar Pei. A biopsy and other viral testing may help differentiate viral plaques from lentigo. Topical or oral antiviral therapies may be used depending on the severity of the lesions.
Causes of Hypopigmentation
Hypopigmentation or depigmentation results in a lightening of the skin (e.g. dark black or brown becomes grey or pink). While there are some benign causes of hypopigmentation, loss of skin color is more concerning if it stems from immune-mediated, infectious, and neoplastic causes.
Similar to hyperpigmentation, any inflammatory cause can result in loss of pigment as well. However, hypopigmentation following inflammation is much less common.
This is an immune-mediated disease that causes loss of pigment in both the skin (leukoderma) and the hair (leukotrichia). Vitiligo generally results in progressive, often symmetrical, loss of pigmentation. Affected areas are generally not inflamed, crusted, or itchy. This disease is confirmed on a biopsy. There are no known treatments, and it is generally considered a cosmetic disease. Certain breeds, including Belgian Tervuren, Rottweilers, and Old English Sheepdogs, are thought to have a hereditary form of vitiligo. Other breeds, like Collies, Doberman Pinschers, Dachshunds, and German Shepherds, have been reported to have a non-hereditary form.
Canine Uveodermatologic Syndrome
This is another immune-mediated disease that results in leukoderma and leukotrichia. The pigmentary changes are most commonly seen on the nose, lips, and around the eyes. However, in addition to cutaneous changes, affected dogs will almost always have ocular changes, including uveitis, which can progress to blindness. The most commonly affected breed is the Akita, which has a genetic basis. Other affected breeds include Alaskan Malamutes, Australian Shepherds, Samoyeds, Siberian Huskies, Shiba Inu, and Chow Chows. Diagnosis of this syndrome requires a skin biopsy and an ocular exam. Treatment with immunosuppressive therapies, like steroids, are important for preventing progression of cutaneous and ocular changes.
Epitheliotropic lymphoma (aka cutaneous lymphoma)
This type of lymphoma is generally confined to the lymphocytes in the skin. Generalized signs, like enlarged lymph nodes, are not usually seen with cutaneous lymphoma. Pigmentary loss with this disease is generally seen on the mucous membranes (lips, gums, eyelids, and nose). Additional clinical signs include red scaly skin, marked itch, and ulcerated nodules and plaques. Cutaneous lymphoma is more common in older dogs. This disease also requires a biopsy for diagnosis. Unfortunately, it has poor long-term prognosis, but chemotherapy and other palliative treatment options are available.
Although many of the processes that cause changes in skin color are benign and result only in cosmetic changes, it is important to discuss any pigment changes with a veterinarian.