216 DISEASES/DISORDERS
Metabolic disorder (e.g., diabetes, superficial necrolytic dermatitis, idiopathic and
iatrogenic hyperadrenocorticism, hypothyroidism)
Cornification/keratinization defects (e.g., seborrhea, vitamin A-responsive dermato-
sis, sebaceous adenitis)
Color dilution alopecia/follicular dysplasia
Immune-mediated diseases (e.g., pemphigus complex, cutaneous lupus erythemato-
sus, vasculitis)
Immunosuppression (e.g., glucocorticoids, chemotherapy, metabolic)
Panniculitis
Nodular dermatosis (e.g., histiocytosis)
DIAGNOSTICS
Identifying Risk Factors
Allergy: flea; atopic dermatitis; cutaneous adverse food reaction; contact dermatitis.
Fungal infection: dermatophytosis.
Endocrine disease: hypothyroidism; hyperadrenocorticism; sex hormone imbalance
or exposure.
Immune incompetency: glucocorticoids; young animals, older debilitated animals.
Seborrhea: acne; schnauzer comedo syndrome.
Conformation: short coat; skinfolds.
Trauma: pressure points; grooming; scratching; rooting behavior; irritants.
Foreign body exposure: foxtail; grass awn.
Diagnostic Tests
Complete physical examination.
Skin scrapings, trichogram.
Dermatophyte culture.
Intradermal allergy testing, restricted antigen food trial.
Endocrine tests.
Blood screen: may be normal or reflect the underlying cause (e.g., anemia secondary
to hypothyroidism; stress leukogram and high serum alkaline phosphatase consistent
with Cushing’s disease; eosinophilia associated with parasitism); chronicity may show
leukocytosis with a left shift and hyperglobulinemia.Skin biopsy.
Cytology: direct smear from intact pustule: neutrophils engulfing bacteria; differen-
tiate bacterial infection from pemphigus foliaceus (acantholytic keratinocytes) and
deep fungal infections (blastomycosis, cryptococcosis); tissue grains may identify fil-
amentous organisms characteristic of higher bacteria.Culture and sensitivity: obtained as an aspirate from intact pustule, swab from the
ventral surface of an epidermal collarette, tissue biopsy, or freshly expressed exudate
from a draining tract or beneath a crust.