Depigmentation Disorders in Dogs: Changing Skin Color
Skin color is determined by melanocyte cells in the skin. Those cells produce melanin which gives skin its color. When skin is exposed to the sun, those cells are stimulated to produce more melanin. That’s how you get a suntan. But what can cause the opposite result? Obviously dogs, like people, come in many different shades. (Dogs can even be albinos – or lacking in pigment altogether.) That means that some dogs are less pigmented to start with. But why might your dog lose that original coloration and develop depigmentation? Let’s discuss some of the possible reasons.
Skin color changing as a result of age
I’m sure you’ve known dogs that go gray as they get older – especially on their faces. According to the Veterinary Internal Medicine textbook, such age-associated graying is a result of decreasing numbers of melanocytes and occurs most frequently in German Shepherds, Labradors, Golden Retrievers and Irish Setters.
Skin color changing as a result season
There are other breeds of dogs that are prone to a seasonal lightening of the nasal planum (the hard, tough, hairless end of their nose). Sometimes referred to as “Snow Nose” these dogs (Siberian Huskies, Labradors and Golden Retrievers) can have darker noses in the summer months and lighter noses in the winter. These same breeds plus German Shepherds, Samoyeds, Afghan Hounds and Dobermans (among others) can also experience a gradual or waxing and lightening or fading of their nose color over time. This condition is known as “Dudley Nose1."
You may know people with vitiligo which, according to Davidson College research, is a progressive disease in which the melanocytes are gradually destroyed causing unpigmented areas on the skin. Dogs can also develop vitiligo. They, too, develop pigment loss from their skin or hair on their heads, but it can occur in other locations too. In some cases, antibodies against melanocytes have been identified in the serum of infected dogs indicating an immune component to the disorder. And skin biopsies of the affected areas will typically reveal a total lack of any remaining melanocytes.
What all three of these causes for depigmentation have is common is the fact that they are not a disease that can bother or hurt your dog at all. There is no reason to worry about them and there is nothing to be done to ‘correct’ them. The depigmentation is purely cosmetic.
Skin color changing as a result of outside influences
For instance, any contact dermatitis/irritation can cause depigmentation as can certain chemicals in rubber that can affect the production of melanin pigment where the rubber touches the skin1. According to the Veterinary Internal Medicine textbook, the administration of certain drugs like ketoconazole, procainamide, and vitamin E have been reported to cause generalized changes in coat color in dogs, and injections of other drugs (glucocorticoids, for instance) can cause localized loss of pigment.
Skin color could be more serious
Hormonal disorders (imbalances of thyroid, adrenal or sex hormones) can alter pigmentation as can bacterial and fungal infections and even cancers (neoplasias). Immune-mediated diseases also occur in dogs where the dog’s own antibodies attack different parts of the skin resulting in depigmentation.
Discoid lupus erythematosus is one such disorder and the second most common immune-mediated disease in dogs. Discoid lupus causes not only depigmentation of the nasal planum but also progresses to the formation of swelling, erosions, ulcers and crusting which are aggravated by UV light exposure; and chronic cases have been reported to develop into squamous cell carcinoma cancers2. Other serious immune-mediated diseases affecting the skin and causing depigmentation include pemphigus erythematosus, systemic lupus erythematosus, pemphigus foliaceus and uveodermatologic syndrome (Vogt-Koyanagi-Harada-Like Syndrome).
The take home message is that changes in your dog’s hair or skin color are often benign changes without any serious consequences to your dog’s overall health. However, sometimes that is not the case and a serious problem needs to be seriously addressed. It is up to you and your veterinarian to evaluate your dog and to perform whatever diagnostic tests are necessary in order to distinguish between the two so that you can respond appropriately.
If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.
1. Ettinger, Stephen J., and Edward C. Feldman. "Veterinary Internal Medicine." Inkling. Elsevier, 2010. Web.
Kimberly D. Morel MD , . Maria C. Garzon MD , in Pediatric Secrets (Fifth Edition) , 2011
136 What conditions are associated with congenital depigmentation of the skin?
Congenital depigmentation , or albinism, constitutes a number of genetically inherited syndromes that are characterized by disorders of melanin synthesis and that may affect the skin, hair, and eyes. Generalized (oculocutaneous) albinism is often complicated by ocular abnormalities, including visual impairment, photophobia, and nystagmus. Piebaldism is a distinct form of congenital depigmentation that affects segments of skin. Patients with this condition often have a forelock of white hair, which is caused by a genetic mutation that differs from generalized albinism. Localized congenital depigmentation associated with a white forelock, heterochromia irides, and congenital deafness characterizes Waardenburg syndrome.
Hypopigmentation and Skin
Hypopigmentation in skin is the result of a reduction in melanin production. Examples of hypopigmentation include:
- Vitiligo: Vitiligo causes smooth, white patches on the skin. In some people, these patches can appear all over the body. It is an autoimmune disorder in which the pigment-producing cells are damaged. There is no cure for vitiligo, but there are several treatments, including cosmetic cover-ups, corticosteroid creams, calcineurin inhibitors (Elidel cream, Protopic ointment) or ultraviolet light treatments. New topical treatments using Janus Kinase inhibitors are being investigated.
- Albinism: Albinism is a rare inherited disorder caused by the absence of an enzyme that produces melanin. This results in a complete lack of pigmentation in skin, hair, and eyes. Albinos have an abnormal gene that restricts the body from producing melanin. There is no cure for albinism. People with albinism should use a sunscreen at all times because they are much more likely to get sun damage and skin cancer. This disorder can occur in any race, but is most common among whites.
- Pigmentation loss as a result of skin damage: If you've had a skin infection, blisters, burns, or other trauma to your skin, you may have a loss of pigmentation in the affected area. The good news with this type of pigment loss is that it's frequently not permanent, but it may take a long time to re-pigment. Cosmetics can be used to cover the area, while the body regenerates the pigment.
My Dog Has Dark Skin Patches — What Is It?
The following is an excerpt from the Petfinder Blog.
Dr. Lauren Brickman writes a pet health and care column for Petside.com. Read all the Q&As she’s shared with Petfinder here.
Q: My Chihuahua is developing dark skin patches under her front leg and on her tail. What causes these black patches?
Could it be fleas?
A: Sometimes these dark patches can be normal. They can occur in areas of friction (under legs, armpits) or they can be normal pigmentation in your dog’s skin that occurs with age.
Dogs with severe skin allergies can develop black patches but the skin in that area is thick, itchy, and almost like elephant skin. That is called lichenification and it is caused by inflammation.
Fleas typically do not cause dark patches but will cause hair loss along the back of the hind legs. Your dog would also be itchy if there were fleas. Make sure to get a good monthly flea preventative from your veterinarian.
If these dark skin patches seem dry or troublesome to your pet, it may be a good idea to have your vet take a look.
What Is Melanin?
In this Article
Melanin is a natural skin pigment. Hair, skin, and eye color in people and animals mostly depends on the type and amount of melanin they have. Special skin cells called melanocytes make melanin.
Everyone has the same number of melanocytes, but some people make more melanin than others. If those cells make just a little bit of melanin, your hair, skin and the iris of your eyes can be very light. If your cells make more, then your hair, skin, and eyes will be darker.
The amount of melanin your body makes depends on your genes. If your parents have a lot or a little skin pigment, youвЂ™ll probably look like them.