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159 Atopic Dermatitis 1405

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Figure 159.3 Marked lichenification and hyperpigmentation
of the periocular skin in a dog with severe atopic dermatitis.
Additionally, hemorrhagic crusts and additional
hyperpigmentation with associated alopecia can be seen along
the dorsal aspect of the muzzle. Facial pruritus was marked in
this patient.

Figure 159.5 Cat with moderate‐to‐severe periocular erythema,
swelling, and self‐induced excoriation from scratching.

or scooting, respectively. In most cases, the dorsal aspect
of the dog is spared, unless concurrent flea allergy der-
matitis is noted (caudal hind end distribution including
rump and tail head). In some dogs, a more widespread
distribution of lesions and pruritus is noted. This may be
seen more commonly in different breeds including
German shepherd, Chinese shar‐pei, and West Highland
white terrier dogs, which have shown phenotypic diver-
sity compared to other dog breeds with more standard
distribution of lesions reflecting atopic dermatitis.
In cats, the distribution pattern and clinical lesions
tend to be less consistent. Cats will, however, generally
Figure 159.4 Salivary staining on the paws of a patient with present with one or more cutaneous reaction patterns:
atopic dermatitis. Moderate erythema can also be appreciated cervicofacial dermatitis (head, neck, pinnal pruritus)
within the interdigital webs of the right front paw. (Figure 159.5), self‐induced noninflammatory alopecia
(Figure 159.6), miliary dermatitis (Figure 159.7) and/or
infections (particularly superficial bacterial pyoderma eosinophilic skin lesions (i.e., eosinophilic plaque)
and dermatophytosis) need to be investigated. (Figure 159.8), eosinophilic granuloma, and indolent
The distribution pattern of lesions and pruritus is most ulcer (Figure 153.9). None of these reaction patterns,
helpful when considering atopic dermatitis. Clinical dis- however, are pathognomonic for allergic skin disease in
ease in dogs most commonly affects ventral sparsely the cat. Other causes of pruritus need to be investigated
haired areas including the abdomen, thorax, inguinal, prior to diagnosing atopic dermatitis. This is especially
and axillary folds. Facial distribution including periocu- true for eosinophilic lesions (particularly plaques and
lar skin and muzzle is also common. The dorsal and ven- indolent ulcers) as these are often manifestations of bac-
tral interdigital webbing of the paws along with the lower terial pyoderma in the cat.
portion of the limbs is often concurrently pruritic; flex- In people, a phenomenon known as the “atopic march”
ural surfaces of the elbows are included in this body has been described where the disease starts with atopic
region. Otitis externa and perianal pruritus are often dermatitis or eczema and progresses to rhinitis and
reported by owners, and may manifest as head shaking asthma. Although the “atopic march” has not been