Page 479 - Cote clinical veterinary advisor dogs and cats 4th

Cornification Disorders 215

GEOGRAPHY AND SEASONALITY
Scaling (formerly called seborrhea sicca) is more
VetBooks.ir humidity). Diseases and Disorders
common in the winter (low environmental
ASSOCIATED DISORDERS
Primary cornification disorders may be associ-
ated with ceruminous otitis externa.
Clinical Presentation
DISEASE FORMS/SUBTYPES
• Primary cornification disorders (usually
hereditary and incurable) or secondary
(acquired, usually curable)
• Generalized or localized
HISTORY, CHIEF COMPLAINT
Owners generally present pets for evaluation
of an unpleasant-appearing, usually scaly or
waxy haircoat or coat with a foul, rancid odor.
PHYSICAL EXAM FINDINGS
• Primary cornification disorders: various
degrees of alopecia and dry scale that may CORNIFICATION DISORDERS Stud tail in a Persian cat. (Copyright Dr. Manon Paradis.)
be focal, multifocal, or generalized over
the trunk. Animals may present with large
hyperkeratotic patches of adherent scale.
Follicular casts (waxy debris surrounding
hair shafts), fronds (clumps of hairs stuck
together like a paintbrush), or severe dandruff
with large flakes may be noted.
• Localized cornification disorders
○ Nasal parakeratosis of the Labrador
retriever: restricted to the nasal planum
○ Nasodigital hyperkeratosis: restricted to
nasal planum and digital pads
○ Ear margin dermatosis: alopecia and
scaling of distal pinnal margins, possibly
associated with fissures
○ Feline acne: comedones on the chin +/−
lips; papules, pustules, erosion, crust, and
pruritus if secondarily infected
○ Tail gland hyperplasia
• Secondary cornification disorders: general
physical findings depend on underlying
cause. Cutaneous findings include a dull
(or waxy) coat with various combinations
of alopecia, scaling, crusting, collarettes, and
excoriations secondary to self-trauma and
pyoderma. CORNIFICATION DISORDERS Ichthyosis in a 5-week-old Shetland sheepdog. (Copyright Dr. Manon Paradis.)
Etiology and Pathophysiology
• Cornification encompasses all the processes DIAGNOSIS
that lead to the formation of the stratum (including Demodex injai, the long-bodied
corneum. This includes keratinization and Diagnostic Overview Demodex mite that has been associated with
formation of the lipid-rich intercellular Scale formation is a common response of the a greasy seborrheic dermatosis, especially in
domain that binds corneocytes to maintain skin to any insult. It is critical to evaluate the adult terriers)
a relatively impermeable barrier. patient for underlying causes—particularly the • Endocrinopathy: hypothyroidism, hyperad-
• Disorders of cornification are due to a roles parasitic and microbial dermatitis may be renocorticism, hyperestrogenism (e.g., Sertoli
defective cornification process or excessive playing if any—before pursuing other causes. cell tumor)
proliferation and/or defective desquamation • Allergic: environmental, dermatologic adverse
(retention hyperkeratosis). Any alteration Differential Diagnosis food reaction (food allergy)
in epidermal turnover times, maturation Secondary cornification disorders; underlying • Management deficiencies: low environmental
processes, and/or desquamation or trans- causes include humidity, inappropriate topical therapy or
epidermal water loss lead to scaling. • Microbial: pyoderma, Malassezia, dermato- frequency, nutritionally inadequate diet
• Other considerations include abnormal phytosis, leishmaniasis (especially if high in phytates and fiber, low
apocrine or sebaceous glandular secretions • Parasitic: flea infestation, cheyletiellosis, sar- in fatty acids)
(in volume or quality). coptic mange, pediculosis, and demodicosis • Metabolic disease (especially liver disease)

www.ExpertConsult.com