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196 Color Disorders of the Skin and Haircoat

• Canine cyclic hematopoiesis: usually lethal • Vitiligo: multifactorial, with genetic cause Advanced or Confirmatory Testing
before age 6 months likely in some cases. Symmetrical depigmen- Additional testing for specific diseases:
VetBooks.ir Clinical Presentation most often on the face (including nose and • Ocular examination (uveodermatologic
tation of hair, skin, and mucosa in patches,
• Endocrine testing (hyperadrenocorticism,
hypothyroidism)
HISTORY, CHIEF COMPLAINT
lips). Affected skin usually looks otherwise
normal. Affects dogs, Siamese cats
syndrome)
Question owners about sun exposure, changes
in health, and inflammation (e.g., pruritus). • Nasal hypopigmentation: noninflammatory • Dermatophyte examination: Wood’s light,
conditions include “snow nose,” in which fungal culture
PHYSICAL EXAM FINDINGS partial symmetrical depigmentation of the • Muscle evaluation (dermatomyositis)
• Note distribution of color change: where on nasal planum occurs, usually in winter • Auditory evaluation (Waardenburg-Klein
body; affecting skin and/or hair? Examine • Nutrition (e.g., reddish-brown coat in black syndrome)
skin for lesions and evidence of inflammation cats due to tyrosine deficiency) • Serologic testing for deep fungal infections,
(e.g., erythema, lichenification). • Lightening of the coat can occur with exces- leishmaniasis
• Certain physical abnormalities are associated sive exposure to chlorinated water, sunlight,
with specific pigmentation disorders (see or in hair cycle arrest (e.g., endocrine disease). TREATMENT
Associated Disorders above). Dark coats can become red or blond.
• Others: drug-induced changes, burns or cold Treatment Overview
Etiology and Pathophysiology injuries, scars The goal is to restore normal pigmentation to
Normal pigmentation is a highly complex Genetic hyperpigmentation or hypopigmenta- skin and hair. Treatment is not always indicated.
process under the influence of numerous genetic tion:
and acquired factors. Both depigmentation and • Hypopigmentation: color dilution alopecia, Chronic Treatment
hyperpigmentation can result from inflamma- oculocutaneous albinism, Waardenburg- Depends on underlying cause:
tory and noninflammatory conditions. Klein syndrome, piebaldism, canine cyclic • Many conditions do not require or respond
hematopoiesis, Chédiak-Higashi syndrome, to treatment.
DIAGNOSIS “Dudley nose” • Inflammation, endocrinopathy, or neoplasia
• Hyperpigmentation: lentigo (e.g., orange may be treatable.
Diagnostic Overview cats) • Uveodermatologic syndrome requires aggres-
Causes of color disorders of dogs and cats are sive therapy to save vision.
myriad. Some are visually distinctive. Initial Database • Reduce sun exposure in hypopigmented dogs.
May include (p. 1091)
Differential Diagnosis • Skin scrapings PROGNOSIS & OUTCOME
Acquired hyperpigmentation: • Skin cytologic examination
• Postinflammatory: very common in dogs but • Skin biopsies: required in many cases, • Good prognosis for cases of acquired color
not cats; can occur with any chronic inflam- particularly with hypopigmentation change if the underlying condition can
matory process but particularly common • Trichography (microscopic examination be controlled; prognosis varies for other
with hypersensitivity disorders, Malassezia of plucked hairs, useful for assessing color conditions.
infection, demodicosis, and pyoderma. In dilution alopecia) • Improvement may be very slow for all
cats, skin hyperpigmentation it is most often • CBC, serum biochemistry profile, urinalysis conditions.
seen with dermatophytosis. Inflammation
can also darken hair color (melanotrichia)
in dogs and in Siamese and Himalayan cats.
• Hormone associated: hyperadrenocorticism,
hypothyroidism, hyperestrogenism
• Neoplasia: feline Bowen disease, other
pigmented tumors
• Acanthosis nigricans in dachshunds: localized
to axillae; a reaction pattern with multiple
causes. Friction, infection, hypersensitivity
are more likely than a primary genetic form.
• Others include alopecia X, recurrent flank
alopecia, sun exposure, drug therapy induced,
papillomavirus-associated plaques, trauma,
and burns.
Acquired hypopigmentation:
• Postinflammatory: less common than
hyperpigmentation but pyoderma, derma-
tomyositis, leishmaniasis, and other inflam-
matory conditions can cause depigmentation
in affected areas (usually haired skin). On
the nasal planum, consider discoid lupus
erythematosus and pemphigus erythemato-
sus, pemphigus foliaceus, uveodermatologic
syndrome, and other immune-mediated
diseases.
Other causes are less common.
• Neoplasia: particularly epitheliotropic lym-
phoma, which can cause striking leukotrichia COLOR DISORDERS OF THE SKIN AND HAIRCOAT Depigmentation of the nasal planum and leukotrichia
and leukoderma. in a golden retriever with epitheliotropic lymphoma.

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