Page 1466 - Clinical Small Animal Internal Medicine

1404 Section 12 Skin and Ear Diseases

reported variable prevalence of the disease, ranging from
VetBooks.ir less than 5% to greater than 25% of the canine population;
true prevalence of disease is uncertain. For the past few
years, atopic dermatitis (or “skin allergies”) has been con-
sistently listed in the top 10 reasons for dogs and cats to
be presented to veterinarians in the United States.

Signalment

Depending on literature cited, age of onset may range
from 4 months to 7 years, though the majority of dogs and
cats with atopic dermatitis will typically start to manifest
clinical disease between 6 months and 3 years of age.
There does not appear to be consensus on whether the
disease is more prevalent in females or males, or whether
sex predilection affects disease development. Although
any breed of dog may be diagnosed with atopic dermatitis,
breed predisposition has been reported due to the genetic
component of disease pathogenesis. More commonly
affected breeds include but are not limited to Boston ter-
rier, boxer, Chinese shar‐pei, Dalmatian, English bulldog, Figure 159.1 Moderately erythematous, coalescing macules in
the inguinal region of a dog with atopic dermatitis.
German shepherd, golden retriever, Labrador retriever,
pug, and West Highland white terrier dogs. Although
genetic involvement has also been noted in cats, no spe-
cific breed predispositions have been identified.

History and Clinical Signs

The hallmark of atopic dermatitis in both dogs and cats
is pruritus, which will often be reported as mild at first
but progresses to become more moderate to severe as
the disease advances. Depending on which specific aller-
gens are involved and/or flare factors in the animal’s par-
ticular environment, pruritus may be present seasonally
or nonseasonally. This may also be affected by geo-
graphic location; in dogs and cats with historically mild
disease, the severity might increase if they move to a
warmer climate where allergen load is higher or different
from what they were exposed to historically. If concur-
rent allergic conjunctivitis or rhinitis is present, serous Figure 159.2 Pinpoint, faint papules on the sternum of a dog with
ocular or nasal discharge, sneezing, or congestion, mild atopic dermatitis.
respectively, may also be present with pruritic skin. In
cats, feline asthma may also be a concurrent finding. Uncommonly, urticarial lesions (hives) may be seen in
In early stages of disease, pruritus may present sine dogs with atopic dermatitis. Salivary staining of the hair
materia, or without concurrent lesions. More often, is commonly noted, particularly in light‐colored
though, dogs without secondary bacterial skin infection dogs, which also supports the presence of pruritus
or yeast overgrowth will present with fairly symmetric, (Figure 159.4).
variably erythematous macules and patches (Figure 159.1) On close physical examination, the clinician will often
or small papular lesions (Figure 159.2). Additionally, find broken pieces of barbered hair stuck between the
signs of self‐trauma may be noted in the form of excoria- gingival tissue and dental arcade, another “clue” that pru-
tions (often linear), hemorrhagic crusts, self‐induced ritus is present. When additional lesions are noted, such
alopecia/barbered hair, hyperpigmentation, and licheni- as pustules, crusts, or epidermal collarettes, alternative
fication (Figure 159.3). disease entities including parasites (Demodex) and