Small Animal Dermatology, 3rd edition

CHAPTER 29 KERATINIZATION (CORNIFICATION) DISORDERS 433

 Primary “seborrhea” (primary keratinization disorder; idiopathic seborrhea and seb-

orrheic dermatitis):

Accelerated epidermopoiesis and hyperproliferation of the epidermis, follicu-

lar infundibulum, and sebaceous gland due more likely to an adaptive response

rather than to a true hereditary cellular defect

American cocker spaniel, English springer spaniel, West Highland white ter-

rier, basset hound, English bulldog, German shepherd dog, doberman pinscher,

Irish setter, Chinese shar-pei, miniature schnauzer, cavalier King Charles spaniel,

dachshund, Labrador retriever

Mild to severe accumulations of scales, crusts, and greasiness; lesions discrete

and focal with thickly crusted plaques and erythema, or diffuse and generalized

(Figures 29.7, 29.8)

Ceruminous otitis externa

Alopecia and erythema, with lichenification, hyperpigmentation, and greasy

exudation

Lesions predominantly truncal

Secondary bacterial folliculitis andMalasseziadermatitis common, especially

in the folds of the ventral neck, axillae, and inguinum; treatment for infection

reduces discomfort and malodor, but does not resolve lesions (Figure 29.9).

 Vitamin A-responsive dermatosis: rare; cocker spaniels, Labrador retrievers, minia-

ture schnauzers, Gordon setters, French bulldogs; clinical signs similar to severe idio-

pathic seborrhea but usually adult onset; hyperkeratotic plaques with follicular plug-

ging and predominant follicular casts; identified by cutaneous biopsy and response

to oral vitamin A supplementation (Figure 29.10).

 Epidermal dysplasia (hyperplastic dermatosis) of West Highland white terrier: often

associated withMalasseziainfection and cutaneous hypersensitivity; may be a cause-

and-effect and not a distinct syndrome; symptoms begin prior to 1 year of age; gener-

alized and severe patches of alopecia, erythema, lichenification, and hyperpigmenta-

tion with greasiness, malodor, and pruritus; lesions begin on the trunk and skinfolds;

otitis externa common (Figure 29.11).

 Generalized sebaceous gland hyperplasia in border collies and wire-haired terriers:

greasy coat along the dorsum.

 Ear margin dermatosis: often secondary to hypothyroidism; primary disorder of

dachshunds; thick and adherent crusts form on the medial and lateral edges of the

pinnae; follicular casts; removal requires effort and produces erosions, pain, and fis-

suring; secondary bacterial folliculitis common (Figure 29.12).

 Acanthosis nigricans: dachshunds; less than 2 years of age; symmetric lesions of

alopecia, striking hyperpigmentation and lichenification beginning in the axillae and

often extending to the ventral neck and inguinum; lesions may generalize further;

secondary bacterial folliculitis andMalasseziadermatitis common (Figure 29.13).

 Nasodigital hyperkeratosis: excessive accumulation of scale and crust on the nasal

planum and footpad margins; possibly a senile change of the cocker spaniel, beagle,

English bulldog, basset hound; lesions generally asymptomatic; cracking and sec-

ondary bacterial infection cause pain; similar in appearance but distinct from nasal