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Causes of Pigment & Color Changes in the Skin & Coat in Dogs
Veterinary & Aquatic Services Department, Drs. Foster & Smith
Skin Conditions
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The skin and coat of a dog may sometimes change color or become lighter or darker. This may be a normal process, or may be due to a serious disease. If the skin or coat has a color other than white, it is said to be 'pigmented.' Colors include brown, black, red, purple, and yellow. If the skin is a darker color than normal, it is said to be 'hyperpigmented.' The table below provides a list of the majority of the conditions, which are associated with pigment change. This extensive listing helps you understand why a quick diagnosis may be difficult to make and various diagnostic tests may need to be performed. The most common conditions causing pigment or color changes are color-coded gray in the table (some may be more common in certain geographical areas).

Condition Description Symptoms Diagnosis Treatment
Acanthosis nigricans Inherited form seen in Dachshunds; secondary form caused by friction, hormonal abnormalities, or hypersensitivities Darkening of the skin; in secondary form see scratching and hair loss History, physical exam; in secondary form, testing to determine underlying cause Primary: No treatment; Secondary: treat underlying disease; in some cases, steroids and Vitamin E supplementation
Adrenal sex hormone responsive dermatosis More common in Pomeranians, Chows, Keeshonden, and Samoyeds Hair loss starts on neck, tail, and back of thighs and progresses to trunk; dog appears to have a 'puppy coat'; skin darkens Biopsy; eliminate other causes Mitotane is optional
Apocrine sweat gland cyst Common Single, round, smooth nodules with no hair; may appear bluish; usually filled with a watery liquid; most common on head, neck, and limbs Physical exam; biopsy Surgical removal is optional
Basal cell tumors Cancerous, slow-growing tumor, which rarely metastasizes; seen in older dogs Single, sometimes fluid-filled nodules, which may ulcerate; usually on the head, neck, and chest; may be hyperpigmented Biopsy Surgical removal
Black hair follicular dysplasia/ alopecia/ dystrophy Rare hereditary disease in dogs with hair of multiple colors; more common in Bearded Collies, Basset Hounds, Salukis, Beagles, Dachshunds, and Pointers Loss of dark or black hair only; symptoms appear between 3 and 6 weeks of age; sometimes scaling Clinical signs, biopsy Shampoos for scaling, if necessary
Bowen's disease A rare type of squamous cell carcinoma in which multiple lesions develop Lesions start out as thickened, dark, raised, and well-delineated; progress to ulcers and crusts and bleed easily; lesions found on the head, neck, shoulder, forelegs, mouth, and genital areas Biopsy Lesions may come and go and are not always treated; some anti-cancer drugs and radiation have been tried with mixed results
Bruises Generally the result of trauma; may indicate abnormally low platelets, clotting problems, or hormonal problems Areas of bluish-black discoloration of the skin Medical history very important; blood tests, if abnormality expected None, if the result of trauma; in other cases, treat underlying cause
Castration responsive dermatosis More common in young unneutered dogs, and in Chows, Samoyeds, Keeshonden, Alaskan Malamutes, Miniature Poodles, and Pomeranians Symmetrical hair loss in genital area and neck; hair loss may progress onto trunk; skin may appear darker; severe scaling; hair color may fade; coat is similar to a 'puppy coat' Physical exam and history; eliminate other causes; blood tests for hormone levels Castration
Chronic irritation/inflammation Chronic atopy, allergies, bacterial infections Darkening and sometimes thickening of the skin History, physical exam; blood tests to rule out other possible causes Treat/remove underlying cause
Color dilution/mutant alopecia Hereditary condition affecting dogs with blue (diluted black) or fawn coat colors; more common in Dobermans, Dachshunds, Great Danes, Yorkshire Terriers, Whippets, and Greyhounds Hair in the blue- and fawn-colored areas starts to thin at around 6 months of age; secondary folliculitis often develops Breed, history, and coat color None; avoid excessive grooming or harsh shampoos; protect skin to prevent secondary bacterial infections
Cushing's disease (hyperadrenocorticism) Caused by an increase in corticosteroids in the body - either due to increased production by the body or as a side effect of high doses or prolonged therapy with corticosteroids Hair loss, thinning of skin, hyperpigmentation, easy bruising, seborrhea, comedones (black heads), may see calcinosis cutis; lethargy, increased thirst and urination, pot-bellied appearance Adrenal gland function tests, urinalysis, chemistry panel, CBC If due to glandular tumors, selegiline, o,p-DDD (Mitotane), or surgical removal of tumor; if due to high steroid doses, withdraw use of steroids slowly
Cyclic (cicatrical) alopecia; seasonal flank alopecia Growth cycle of hair stops at certain times of the year Symmetrical hair loss with definite borders; usually on back and flanks; skin may become darker History, clinical signs, biopsy None
Demodectic mange (red mange, puppy mange) Infection with the Demodex mite - occurs when the immune system is deficient Hair loss, scaliness, redness, pustules, ulcers, sometimes itching, darkening of the skin Skin scraping and microscopic examination NO Steroids
Amitraz (Mitaban) dips
Epitheliotrophic lymphoma (mycosis fungoides) Rare cancer of T lymphocytes seen in older dogs Can take multiple forms: redness with itching and scale; ulcers and loss of pigment; one or more nodules; oral ulcers Needle or other biopsy Poor response to treatments, which include chemotherapy, surgical removal, retinoids, fatty acids
Estrogen responsive dermatosis (ovarian imbalance type II) More common in young spayed dogs, and in Dachshunds and Boxers Hair loss starting at the genital area and flanks and moving forward; hair color may fade; coat is similar to a 'puppy coat' Physical exam and history; eliminate other causes; response to therapy Estrogen replacement therapy; caution - can have severe side effects
Follicular cyst Most common cyst; may be called 'sebaceous cysts' by some veterinarians Single round nodules on or underneath the skin; may appear bluish; may contain a thick, yellowish to gray material; usually found on the head, neck, and trunk Biopsy Surgical removal optional; do NOT squeeze these cysts, since a severe skin reaction will occur
Follicular dysplasia (non-color linked) Patchy hair loss of unknown cause seen in the Siberian Husky, Doberman Pinscher, Airedale, Boxer, Staffordshire Bull Terrier, Curly Coated Retriever, Irish Water Spaniel, and Portuguese Water Dog In Huskies, hair loss on the body, reddish tinge to hair; in Dobermans, hair loss over lumbar area; in Boxers and Terriers, hair loss over lumbar area, skin may be hyperpigmented; in Retrievers and Spaniels, loss of guard hairs on back and trunk and secondary hairs are dull and lighter in color; Breed, biopsy None
Growth hormone responsive alopecia Not well understood; thought to be caused by an enzyme deficiency or decrease of adrenal hormones, which allows certain other hormones to accumulate in the body: more common in Pomeranians, Chow Chows, Keeshonden, Samoyeds, and Poodles Hair loss on neck, tail, and the back of the thighs; skin darkens; usually starts when dog is less than two years old Hormonal blood testing Neuter animal; growth hormone; hormonal supplementation
Hemangiosarcoma Malignant, invasive tumor more common on sun-damaged skin Blue to reddish black nodule; usually on chest or abdomen; often ulcerate Biopsy Surgical removal; need to remove large area around the tumor; if tumor is on a leg, amputation of the leg is commonly recommended
Hyperestrogenism (ovarian imbalance type I) Rare disease in which female animals have excess levels of estrogen; can be caused by cancer of the ovaries Symmetrical loss of hair; hair pulls out easily; darkening of the skin; enlarged nipples and vulva; may rarely see seborrhea and itching History, physical exam, rule out other causes of hair loss, measure blood estrogen levels Spay; look for metastasis to the lungs
Hypothyroidism Decreased production of thyroid hormone; most common hormonal disease affecting the skin in dogs Hair loss, dry and brittle hair, seborrhea; secondary bacterial and yeast infections; lethargy, obesity, slow heart rate; changes in skin pigmentation may occur Thyroid gland function tests, chemistry panel, CBC Lifetime thyroid supplementation
Injection site alopecia Hair loss at the site of an injection of a medication or vaccine; skin may become thickened; in cats, ulcers may develop Hair loss occurs several months after injection; area may become hyperpigmented History and physical examination None; the condition is permanent
Interstitial cell tumor Tumor of the testicle; may not cause any skin changes If skin changes occur, See Seborrhea, loss of hair on the trunk, enlargement of the tail gland and perianal glands; may see increased pigment in the skin Biopsy Castration; anti-seborrheic shampoos
Jaundice Generally results from liver disease Yellowing of the skin, mucous membranes, and whites of the eyes Physical exam; blood tests to assess liver function Treatment of underlying liver disease
Lentigo Inherited in Pugs Circular brownish-black areas of coloration Physical exam; skin biopsy to rule out other causes of hyperpigmentation None
Malassezia Usually follows some other underlying disease Itching, redness, hair loss, greasy scales; if chronic, develop hyperpigmentation Skin scraping/smear and microscopic examination, culture Treat underlying disease; oral ketoconazole; miconazole shampoos
Mast cell tumor Common cancer which is graded from 1-4: Grade 1 is slow-growing tumors, and Grade 4 is rapidly growing malignant tumors with metastases Tumors may be of various sizes, appearances, and numbers Biopsy to grade the tumors, which determines treatment and prognosis Depends upon grade; surgical removal, taking large area around tumor; chemotherapy; prednisone; radiation
Melanoma Malignant tumor of older dogs Usually single dark-colored nodule, which often ulcerates Biopsy Surgical removal, taking large area around tumor
Nasal depigmentation (Dudley nose) Previous black nose turns chocolate brown to light pink; more common in Yellow Labs, Golden Retrievers, Poodles, and Dobermans; not associated with a disease process Progressive fading of color of nose with no other signs such as crusting or ulceration Physical exam None
Pemphigus foliaceus The most common form of pemphigus in the dog; an autoimmune disease; some breeds are at increased risk Often affects feet and head; starts with pustules and progresses to severe crusting; depigmentation of the nose is common; itching may occur; if footpads and nails affected often see lameness; symptoms wax and wane; severely affected animals may have fever and loss of appetite History, physical exam, skin scraping, and biopsy Corticosteroids, other immunosuppressive therapy, gold injections
Red/brown staining of hair Often caused by body secretions such as tears and saliva from licking Light colored hair turns a reddish brown Clinical signs, history Treat underlying condition
Rocky mountain spotted fever Caused by an organism spread by ticks; skin lesions are not always present Fever, loss of appetite, depression, pain in joints, edema, hemorrhages under the skin (appear as bruises), ulceration of mucous membranes and extremities Special blood tests to detect the organism or antibodies to it; biopsy Antibiotics and supportive care
Sertoli cell tumor Tumor of the testicles in middle-aged dogs Male dogs take on female sexual characteristics; hair loss, increased skin pigment, reddened area on prepuce Physical exam Castration
Skin cancer See specific type, e.g.; Basal cell tumor, Melanoma, Mast cell tumor      
Tail dock neuroma Nerve regrowth after tail docking causes symptoms Nodule at site of docking, itching with self-mutilation, hair loss, and hyperpigmentation History and symptoms Surgical removal
Tail gland hyperplasia Dogs have a sebaceous gland on the top of the tail near its base; in this disorder, the gland enlarges; seen in unneutered dogs and secondary to other diseases such as hypothyroidism Oily area, hair loss, crusts, and hyperpigmentation on area over gland Clinical signs; look for underlying cause Castration may help; treat underlying cause; surgical removal
Uveodermatologic syndrome Hypersensitivity to melanin (the dark pigment) in the skin and eyes Pigment loss on nose, lips, and eyelids; occasionally footpads, scrotum, and anus can be affected; rarely see ulcers or drainage; uveitis (inflammation of the eye) may occur History, clinical signs, biopsy Long-term prednisone, azathiprine; appropriate eye medications
Vitiligo (Decreased Pigment) Can be hereditary or caused by an autoimmune reaction Loss of pigment, which may be temporary or permanent; usually on nose, lips, and face Clinical signs, skin biopsy None
 
References and Further Reading

Practice. W.B. Saunders Co. Philadelphia, PA; 1994.

Greene, CE (ed.) Infectious Diseases of the Dog and Cat. W.B. Saunders Co. Philadelphia, PA; 1998.

Griffin, C; Kwochka, K; Macdonald, J. Current Veterinary Dermatology. Mosby Publications. Linn, MO; 1993.

McKeever, PJ; Harvey, RG. Skin Diseases of the Dog and Cat. Iowa State University Press. Ames, Iowa; 1998.

Paterson, S. Skin Diseases of the Cat. Blackwell Science Ltd. London, England; 2000.

Paterson, S. Skin Diseases of the Dog. Blackwell Science Ltd. London, England; 1998.

Scott, D; Miller, W; Griffin, C. Muller and Kirk's Small Animal Dermatology. W.B. Saunders Co. Philadelphia, PA; 1995.

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