Page 66 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Inflammatory Lesions
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6.9 Pemphigus foliaceus (PF)
VetBooks.ir Autoimmune blistering process caused by the production of autoantibodies against antigens on

the surface of the keratinocytes of the epidermis.

Clinical features
• Uncommon condition in dogs and cats.
• Average age in dogs is 4 years with two-thirds of subjects developing lesions at or be-
fore 5 years of age. Age predilection not reported in cats.
• It presents in the form of pustules or crusts of variable sizes and colours. They are lo-
cated on the muzzle, planum nasale, pinnae, periorbital area and distal extremities, in-
cluding paw pads. In dogs, the nose often appears inflamed and depigmented with crusts;
trunk, ventral abdomen, scrotum and mucucutaneous junctions can also be involved.
• Causes of pemphigus foliaceus are mostly unknown. Some cases have been linked to
chronic skin disease and allergy. In cats, a drug-related PF-like condition has been
described after administration of selected antibiotics and methimazole.
• Pemphigus foliaceus is a progressive disease with variable response to treatment.
• Over-represented canine breeds: Bearded Collie, Akita, Chow Chow, Newfoundland,
Schipperke, Dobermann, English Springer Spaniel, Shar Pei and Collie.

Cytological features
• Cellularity is variable, often good.
• Background: variably haemodiluted.
• Variable numbers of acantholytic keratinocytes, characterized by a moderate to abundant
amount of basophilic cytoplasm. The cell borders are rounded. Nuclei are round, centrally
located, often showing a single prominent nucleolus.
• High numbers of non-degenerate neutrophils are often present. These cells can be found encirc-
ling the acantholytic cells.
• Eosinophils are present in about half of the dogs with PF.

Differential diagnosis
Bacterial superficial folliculitis

Pearls and Pitfalls
• In order to increase the chances of identifying acantolytic cells, impression smears from the
inner surface of the crusts are preferred over the exclusive cytological examination of the
purulent material. For similar reasons, when incisional biopsies are taken, early lesions (e.g.
pustules and vesicopustules) should be included.
• Other less common forms of pemphigus (e.g. pemphigus vulgaris, pemphigus erythemato-
sus) have been reported in the dog and the cat. These are cytologically indistinguishable from
pemphigus foliaceus and definitive diagnosis relies on clinical and histopathological findings.
• Acantolytic cells are not pathognomonic for pemphigus and can also be found in association
with other types of inflammatory skin diseases and neoplasia.