Causes of Pigment & Color Changes in the Skin & Coat
Holly Frisby, DVM, MS
Veterinary Services Department, Drs. Foster & Smith, Inc.
The skin and coat of a cat 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, purplish-blue, and yellow. If the skin is a darker color than normal, it is said to be 'hyperpigmented.' The list 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.
Apocrine sweat gland cyst
Description: Rare in cats.
Symptoms: Single, round, smooth nodules with no hair; may appear bluish; usually filled with a watery liquid; most common on head, neck, and limbs.
Diagnosis: Physical exam; biopsy.
Treatment: Surgical removal is optional.
Basal cell tumors
Description: Most common skin tumor in cats; benign tumors; may become cancerous, slow-growing tumors which rarely metastasize.
Symptoms: Single, sometimes fluid-filled nodules which may ulcerate; usually on the head, neck, and chest; may be hyperpigmented.
Diagnosis: Biopsy.
Treatment: Surgical removal (if benign, surgical removal is optional.)
Basal cell tumors
Description: Most common skin tumor in cats; benign tumors; may become cancerous, slow-growing tumors which rarely metastasize.
Symptoms: Single, sometimes fluid-filled nodules which may ulcerate; usually on the head, neck, and chest; may be hyperpigmented.
Diagnosis: Biopsy.
Treatment: Surgical removal (if benign, surgical removal is optional.)
Bowen's disease
Description: A rare type of squamous cell carcinoma in which multiple lesions develop.
Symptoms: Lesions start out as thickened, dark, raised, and well-delineated; progress to ulcers and crusts and bleed easily; found on the head, neck, shoulders, and forelegs.
Diagnosis: Biopsy.
Treatment: Lesions may come and go and are not always treated; some anti-cancer drugs and radiation have been tried with mixed results.
Bruises
Description: Generally the result of trauma; may indicate abnormally low platelets, clotting problems, or hormonal problems.
Symptoms: Areas of bluish black discoloration of the skin.
Diagnosis: Medical history very important; blood tests if abnormality expected.
Treatment: None, if the result of trauma; in other cases, treat underlying cause.
Chronic irritation/inflammation
Description: Chronic atopy, allergies, bacterial infections.
Symptoms: Darkening and sometimes thickening of the skin.
Diagnosis: History, physical exam; blood tests to determine cause.
Treatment: Treat/remove underlying cause.
Cushing's disease (hyperadrenocorticism)
Description: 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.
Symptoms: Hair loss, thinning of skin, hyperpigmentation, easy bruising, seborrhea, comedones (black heads); lethargy, increased thirst and urination, pot-bellied appearance.
Diagnosis: Adrenal gland function tests, urinalysis, chemistry panel, CBC.
Treatment: 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.
Epitheliotropic lymphoma (mycosis fungoides)
Description: Rare cancer of T lymphocytes seen in older cats; may be associated with FeLV.
Symptoms: Redness, itching, scales, ulcerated nodules.
Diagnosis: Needle or other biopsy.
Treatment: Poor response to treatments which include chemotherapy, surgical removal, retinoids, fatty acids.
Follicular cyst
Description: Most common cyst; may be called "sebaceous cysts" by some veterinarians.
Symptoms: 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.
Diagnosis: Biopsy.
Treatment: Surgical removal optional; do NOT squeeze these cysts since a severe skin reaction will occur.
Hemangiosarcoma
Description: Malignant, invasive tumor more common on sun-damaged skin.
Symptoms: Blue to reddish black nodule; usually on ears, head, legs, groin, and axillae; often ulcerate.
Diagnosis: Biopsy.
Treatment: Surgical removal; need to remove large area around the tumor; if tumor is on a leg, amputation of the leg is commonly recommended.
Hypothyroidism
Description: Decreased production of thyroid hormone; uncommon in cats.
Symptoms: Dry and brittle hair, seborrhea; secondary bacterial and yeast infections; lethargy, obesity, slow heart rate; changes in skin pigmentation may occur.
Diagnosis: Thyroid gland function tests, chemistry panel, CBC.
Treatment: Lifetime thyroid supplementation.
Injection site alopecia
Description: Hair loss at the site of an injection of a medication or vaccine; skin may become thickened; in cats, ulcers may develop.
Symptoms: Hair loss occurs several months after injection; area may become hyperpigmented.
Diagnosis: History and physical examination.
Treatment: None; the condition is permanent.
Jaundice
Description: Generally results from liver disease.
Symptoms: Yellowing of the skin, mucous membranes and whites of the eyes.
Diagnosis: Physical exam; blood tests to assess liver function.
Treatment: Treatment of underlying liver disease.
Lentigo
Description: Common on the lips and nose of orange cats.
Symptoms: Circular brownish-black areas of coloration.
Diagnosis: Physical exam; skin biopsy to rule out other causes of hyperpigmentation.
Treatment: None.
Malassezia
Description: Usually follows some other underlying disease.
Symptoms: Itching, redness, hair loss, greasy scales; if chronic develop hyperpigmentation.
Diagnosis: Skin scraping/smear and microscopic examination, culture.
Treatment: Treat underlying disease; oral ketoconazole; miconazole shampoos.
Mast cell tumor
Description: Common cancer which is graded from 1-4: Grade 1 is one slow-growing tumor, and Grade 4 is rapidly growing malignant tumors with metastasis; in cats, most are Grade 1.
Symptoms: Tumors may be of various sizes, appearances, and numbers.
Diagnosis: Biopsy to grade the tumors which determines treatment and prognosis.
Treatment: Depends upon grade; surgical removal, taking large area around tumor; chemotherapy; prednisone; radiation.
Melanoma
Description: Malignant tumor; uncommon in cats.
Symptoms: Usually single, dark-colored nodule which often ulcerates.
Diagnosis: Biopsy.
Treatment: Surgical removal, taking large area around tumor.
Mosquito bite hypersensitivity
Description: Severe allergic reaction to mosquito bites; lesions most common on nose and ear tips — also footpads, lips, and chin.
Symptoms: Acute lesions are red, raised, and oozing; with time develop hair loss, scales, nodules, and pigment changes; some cats develop fever and swollen lymph nodes.
Diagnosis: History of exposure to mosquitoes; lesions resolve when cat is hospitalized or otherwise restricted from exposure to mosquitoes.
Treatment: Restrict exposure to mosquitoes, insect repellents, prednisone.
Pemphigus foliaceus
Description: The most common form of pemphigus in the cat; an autoimmune disease.
Symptoms: 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 cats may have fever and loss of appetite.
Diagnosis: History, physical exam, skin scraping and biopsy.
Treatment: Corticosteroids, other immunosuppressive therapy, gold injections.
Post-clipping change in hair color (feline acromelanism)
Description: More common in Siamese, Burmese, Himalayan, and Balinese; in these breeds, skin at higher temperatures has lighter colored hair, and cooler areas have darker hair; when area is clipped, it is cooler and hair grows in darker.
Symptoms: Hair in a clipped area grows in with a darker color; after the next shed the hair returns to its normal color.
Diagnosis: Breed, history.
Treatment: None.
Red/brown staining of hair
Description: Often caused by body secretions such as tears and saliva from licking.
Symptoms: Light colored hair turns a reddish brown.
Diagnosis: Clinical signs, history.
Treatment: Treat underlying condition.
Skin cancer
See specific type, e.g., Basal cell tumor, Mast cell tumor, Melanoma.
Stud tail (tail gland hyperplasia)
Description: A sebaceous gland (on the top of the tail near its base) enlarges; most often occurs in confined, unneutered males.
Symptoms: Oily area, hair loss, and crusts on area over gland; may become hyperpigmented.
Diagnosis: Clinical signs.
Treatment: Castration usually does not resolve the condition; antiseborrheic shampoos, retinoids; if confined, allow cat more freedom.
Vitiligo (decreased pigment)
Description: Can be hereditary or caused by an autoimmune reaction.
Symptoms: Loss of pigment which may be temporary or permanent; usually on nose, lips, and face.
Diagnosis: Clinical signs, skin biopsy.
Treatment: None.
* off-label use: medication used to treat a condition for which it was not developed (or licensed). A large number of medications fall under this category. Research has almost always been performed to determine the effectiveness and safety of the product, but the manufacturer has not undertaken the lengthy process required for licensure.
References
Birchard, SJ; Sherding, RG (eds) Saunders Manual of Small Animal 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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