Small Animal Dermatology, 3rd edition

436 DISEASES/DISORDERS

CLINICAL FEATURES

 Syndromes may be visually distinctive or appear very similar.

 Focal or generalized, visible accumulations of epidermal debris.

 Small scales or large rafts of keratin.

 Excessive greasiness.

 Lichenification and hyperpigmentation with chronicity.

 Thickening of the footpads or nasal planum.

 Erosions beneath adherent keratinaceous debris.

 Fissures within thick crusts.

 Ceruminous otitis externa.

 Follicular casts.

 Comedones.

 Malodor.

 Variable pruritus leading to excoriation.

 Secondary bacterial folliculitis orMalasseziadermatitis.

 Nondermatologic symptoms dependent on etiology.

DIFFERENTIAL DIAGNOSIS

 Often based on the following criteria:
Signalment and history: paramount in distinguishing the possible causes of ker-

atinization defect

Presence or absence of pruritus: noted with cutaneous hypersensitivity; primary

keratinization defects often not pruritic unless secondary bacterial folliculitis or

Malasseziadermatitis develops

Concurrent signs: lethargy, weight gain, polyuria/polydipsia, reproductive fail-

ure, change in body conformation, lack of hair regrowth

Response to therapy: antibiotics, antiyeast medication, thyroid supplementation.

 Differentiation between primary and secondary keratinization disorders based on

exclusion of underlying etiology and dermatohistopathology results.

DIAGNOSTICS

 CBC/biochemistries/urinalysis: usually normal with primary keratinization disor-

ders; mild, nonregenerative anemia and hypercholesterolemia (hypothyroidism);

neutrophilia, monocytosis, eosinopenia, lymphopenia, elevated serum alkaline phos-

phatase, hypercholesterolemia, and hyposthenuria (hyperadrenocorticism).

 Thyroid hormone levels and adrenal function tests: see specific chapters for test rec-

ommendations.

 Skin scraping: ectoparasitism.

 Intradermal allergy test: atopy.

 Restricted-ingredient food trial: cutaneous adverse food reaction.