CLINICAL SIGNS
2. Crusts from ruptured pustules on a dog's nasal planum and dorsal nasal region.
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The earliest lesions of pemphigus foliaceus consist of erythematous macules that then progress rapidly to a pustular stage.
Pustules tend to be large, irregular, and coalescing (Figure 1). Multiple hair shafts protruding from pustules are more consistent with pemphigus foliaceus and help differentiate pemphigus
foliaceus from the more common cause of pustules, bacterial folliculitis.38 Because pustules are fragile and easily ruptured, only crusts or the dried exudate from ruptured pustules may be noted (Figure 2). For this reason, crusts rather than pustules are the most commonly seen lesion in cases of pemphigus foliaceus.4,5,14
3. Ulceration from a deep pyoderma in a patient with pemphigus foliaceus. Ulcers should not be seen in pemphigus foliaceus
patients unless another condition such as a pyoderma is present. Note the symmetrical appearance of the facial lesions.
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Erosions can be noted, especially if a crust is removed. Ulcers are rare because pemphigus foliaceus is a superficial epidermal
skin disease. Ulcers can be seen in cases of pemphigus foliaceus that have a concurrent condition that affects the deeper
sections of skin such as a deep pyoderma (Figure 3). Rarely, erosions, crusts, and pustules can be grouped into an annular or polycyclic pattern. Pemphigus foliaceus lesions
typically have a waxing and waning course. Lesions are usually bilateral and symmetrical.
Lesions on the concave pinnae should increase your clinical suspicion of pemphigus foliaceus since few other pustular conditions
affect the concave pinnae (Figure 4). Mucosal lesions are rare in pemphigus foliaceus.
4. Crusts and dried exudate on the concave pinna of a dog with pemphigus foliaceus. (Photo courtesy of Lauren Pinchbeck, DVM,
DACVD.)
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In most dogs, lesions initially appear on the face (the dorsal muzzle, planum nasale, periocular skin, and ears) and then
regionalize or generalize over the course of months. Rarely, some dogs will either start with a generalized distribution or
have only a localized form of the disease.
In dog and cats with generalized pemphigus foliaceus lesions, widespread erythema and exfoliation can be noted. Massive exfoliation,
especially if extending beyond the borders of the original lesions, is more suggestive of bacterial infections than pemphigus
foliaceus. Systemic signs such as fever, lethargy, anorexia, and lymphadenopathy can occur with pemphigus foliaceus.15,33 Systemic signs seem more common in patients with generalized lesions. Pruritus, especially in patients with generalized
disease, is variable in dogs and cats with pemphigus foliaceus.5,14,15 Careful questioning of a pet owner can reveal whether the skin lesions developed before the pruritus. This timing of lesion
development is in contrast to allergies, which usually start with pruritus.
5. Crusts on the footpads of a dog with pemphigus foliaceus.
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Canine pemphigus foliaceus can involve the footpads along with other sites on the body. Rarely, canine pemphigus foliaceus
is localized only to the footpads. Pustules are only rarely seen on the footpads, probably because the pustules rupture while
the patient walks. Clinically, pemphigus foliaceus on the footpads results in lameness and hyperkeratosis (Figure 5).39,40 Canine pemphigus foliaceus can also rarely occur just around the claws.41
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