CHAPTER 29 KERATINIZATION (CORNIFICATION) DISORDERS 435
erythema, and erosions on distal extremities and mucocutaneous junctions; asso-
ciated with mental dullness, behavior abnormalities, diarrhea, bronchopneumonia,
arched hard palate, secondary bacterial folliculitis, andMalasseziadermatitis; pinnal
lesions and otitis externa.Facial dermatitis of Persian and Himalayan cats: greasy, adherent debris accumulates
in facial and nasal folds; ceruminous otitis externa, secondary bacterial folliculitis,
andMalasseziadermatitis, significant pruritus; begins between 10 months and 6 years
of age (Figure 29.27).Primary seborrhea in newborn Persian kittens.
Secondary Keratinization Disorders
Cutaneous hypersensitivity: atopy, flea allergic dermatitis, food allergy, and contact
dermatitis; pruritus, secondary skin trauma and irritation.
Ectoparasitism: scabies, demodicosis, and cheyletiellosis; inflammation and exfolia-
tion (Figure 29.28).
Bacterial folliculitis: bacterial enzymatic disadhesion and increased exfoliation of cor-
neocytes in the attempt to shed pathogenic organisms (Figure 29.29).
Dermatophytosis: usually exfoliative; increased shedding of infected corneocytes as
primary skin mechanism in resolving fungal infection (Figure 29.30).
Endocrinopathy:
Hypothyroidism: abnormal keratinization resulting in accumulation of scales,
symmetric patches of alopecia, excessive sebum production; hyperpigmentation;
secondary bacterial folliculitis andMalasseziadermatitis (Figure 29.31)
Hyperadrenocorticism: abnormal keratinization and decreased follicular activ-ity; excessive scaling and secondary bacterial folliculitis; calcinosis cutis initially
seen as firm, white plaques with scale (Figure 29.32)
Other hormonal abnormalities (e.g., sex hormone abnormalities, hyperthy-roidism, and diabetes mellitus) associated with excessive scaling from metabolic
abnormalities.Age: geriatric animals may have a dull, brittle, and scaly hair coat; alterations caused
by natural changes in epidermal metabolism associated with age; no specific defect
identified.Nutritional disorders: malnutrition and generic dog food dermatosis; scaling from
abnormalities in keratinization (Figure 29.33).
Autoimmune dermatoses: pemphigus complex – may appear exfoliative: vesicles
become scaly and crusty; lupus erythematosus – cutaneous signs often appear as areas
of alopecia and scaling (Figure 29.34).Neoplasia: primary epidermal neoplasia (epitheliotropic lymphoma); alopecia and
scaling from epidermal structures damaged by infiltrating lymphocytes; preneoplastic
conditions (actinic keratosis) initially appear exfoliative (Figure 29.35).Miscellaneous: any disease process may result in excessive scale formation owing to
metabolic dyscrasia or cutaneous inflammation.
Exfoliative disorders: rare in cats: tail gland hyperplasia, thymoma-associated exfo-
liative dermatitis (Figure 29.36).