Causes of Scaliness of the Skin
Holly Frisby, DVM, MS
Veterinary Services Department, Drs. Foster & Smith, Inc.
Scaliness of the skin, which can look like dandruff may simply be caused by dry skin, however, there are many other causes, some of them serious. Many of the conditions which can cause scaliness are described in the list below. This is a long list, so you can understand why a quick diagnosis may be difficult to make and various diagnostic tests may need to be performed.
Cheyletiella (rabbit fur mite) mange
Description: Infection with the Cheyletiella mite.
Symptoms: Itching, scaliness; some hair loss, if severe.
Diagnosis: Skin scraping and microscopic examination — the mite is often very difficult to find.
Treatment: Pyrethrin.
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.
Demodectic mange
Description: Infection may be localized or generalized; the generalized form occurs in cats who have a deficient immune system.
Symptoms: Hair loss, scaliness, redness, sometimes itching.
Diagnosis: Skin scraping and microscopic examination.
Treatment: NO Steroids! Rotenone, dilute Amitraz (Mitaban) dips, lime sulfur dips, ivermectin (off-label use*).
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.
Flea allergy dermatitis (flea bite hypersensitivity)
Description: Severe reaction by the cat to the saliva of the flea.
Symptoms: Intense itching, redness, hair loss papules, crusts and scales; sometimes development of infection or hot spots.
Diagnosis: Presence of fleas; reaction to intradermal testing.
Treatment: Flea Control in the environment and on the cat; steroids and antihistamines for the itching.
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.
Ichthyosis (fish scale disease)
Description: Very rare.
Symptoms: Excessive thickening and crusting of skin and foot pads; seborrhea; odor; symptoms start in kittens.
Diagnosis: Biopsy.
Treatment: Difficult to treat; intense, lifetime management required; treat seborrhea; retinoids.
Lupus erythematosus
Description: Autoimmune disease affecting many body systems inlcuding joints, kidneys, muscles, nervous system.
Symptoms: Skin lesions may include thickening or ulcers of the foot pads, scaling, and recurring bacterial infections with pustules.
Diagnosis: Special blood tests (LE test); biopsy.
Treatment: Prednisone and other immunosuppressive drugs; treat underlying infections.
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.
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.
Pituitary dwarfism
Description: Hereditary condition in which the pituitary gland does not produce the necessary hormones.
Symptoms: Kittens fail to grow; cats may develop seborrhea, rarely have other signs.
Diagnosis: Special blood testing for the presence of certain hormones.
Treatment: Hormone replacement therapy.
Ringworm
Description: Infection with several types of fungus.
Symptoms: Hair loss, scaliness, crusty areas; some itching.
Diagnosis: Culture.
Treatment: Miconazole, lime sulfur dips; oral griseofulvin or itraconazole; ringworm vaccine.
Sebaceous adenitis
Description: Sebaceous glands are destroyed, cause unknown; very rare in cats.
Symptoms: Circular areas of crusts and scales on head, ears, and neck; hair pulls out easily, leaving skin exposed.
Diagnosis: Clinical signs, skin biopsy.
Treatment: Antiseborrheic shampoos, fatty acid supplements; in more severe cases, steroids, retinoids.
Seborrhea
Description: Can be primary (inherited) or secondary (resulting from other disease processes such as FeLV, FIP, FIV, ringworm, and parasites.)
Symptoms: Scales; depending upon the type, may have a dry or oily coat; odor; some scratching; may see hair loss.
Diagnosis: Blood tests, skin scrapings, etc. to find underlying cause.
Treatment: Treat underlying cause if present; antiseborrheic shampoos; fatty acid supplements.
Solar dermatosis
Description: Skin reaction to sunlight; more common in cats with white ears.
Symptoms: Redness, hair loss, and scaling on nose and ears, later crusts and ulcers.
Diagnosis: History, breed, physical exam, skin biopsy.
Treatment: Must avoid further sun exposure, especially from 9 am to 3 pm; sunblock, steroids.
* 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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