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162 Autoimmune and Immune‐Mediated Skin Diseases 1429

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Figure 162.7 Cocker spaniel with pemphigus foliaceus. Multifocal
to coalescing lesions covered with yellowish crusts localized to the
pinna, dorsal aspect of the head and muzzle. Areas of erosion are
noted where adherent crusts were removed. Source: Courtesy of
Sheila Torres.

Figure 162.6 Sample collected from a pustule in a case of
pemphigus foliaceus. The arrow shows a characteristic
acantholytic cell. Also present are large numbers of neutrophils
and eosinophils. Source: Courtesy of Lisa Reiter.

are the ideal lesions to biopsy. Periodic acid–Schiff (PAS)
stain should be requested to evaluate the sample for fun-
gal elements. Immunofluorescence or immunohisto-
chemistry is rarely used to support a diagnosis.

Pemphigus Foliaceus
Pemphigus foliaceus (PF) is a fairly common autoim-
mune disease that affects many species, including dogs
and cats. The disease affects middle‐aged to older ani-
mals. No sex predilection has been recognized.
Dogs may develop large pustules, erosions and crusts
on the face (particularly the periocular region and bridge
of the nose), concave aspect of the pinnae, pawpads, and/
or trunk (Figure 162.7). Pruritus may or may not be pre-
sent. Pemphigus foliaceus in cats is characterized by
crusting on the pinnae, face, and/or nailfolds. Caseous Figure 162.8 Domestic shorthair cat with caseous debris and
debris may also be present around the nails (Figure 162.8). erythema of the nailfold associated with pemphigus foliaceus.
Pruritus is usually absent.
The reader is referred to the pemphigus introduction Glucocorticoids are generally effective but often need
above for details about biopsy technique and special test- to be combined with azathioprine. Glucocorticoids can
ing. Histopathology reveals broad, subcorneal pustules also be combined with ciclosporin, chlorambucil, or tet-
with acantholytic keratinocytes. Differential diagnoses racycline with niacinamide (see Table 162.1).
include superficial pyoderma, pustular dermatophytosis, Topical flea and tick products that contain amitraz
and drug reactions. Complications include fever, weight have been associated with pemphigus‐like disease. The
loss, lethargy, and anorexia in pets that have widespread first step in treatment should be to discontinue amitraz‐
lesions. Concurrent dermatophytosis and/or secondary containing flea/tick preventives. Immunosuppressive
pyoderma may also be present. therapy should then be started.