Skin lesions raised clinical suspicion for a condition other than allergic hypersensitivity with secondary bacterial pyoderma. Differential diagnoses included pemphigus foliaceus (an autoimmune skin disease), other immune-mediated skin diseases, cutaneous histiocytosis, and epitheliotropic lymphoma.
Cytologic examination of skin pustules revealed marked neutrophilic and eosinophilic inflammation, rare cocci, and occasional rounded keratinocytes consistent with acantholytic cells. Pemphigus foliaceus was suspected based on clinical and cytologic findings. A second biopsy was recommended because of nonspecific initial histopathology results.
Two weeks after initial presentation to the dermatology clinic, Hope was anesthetized with IV butorphanol and propofol, and biopsy was performed. A combined injection of articaine HCl and epinephrine was administered subcutaneously at biopsy sites for analgesia. An 8-mm punch was used to obtain biopsies from 5 representative sites on the neck, dorsum, and edematous lateral limbs; one biopsy was submitted for fungal and aerobic bacterial culture. Hyperkeratotic crusts from the paw pads were also submitted for evaluation. Biopsy sites healed without complication.
Histopathology of the neck, dorsum, and limb biopsies revealed severe, chronic, hyperplastic, subcorneal crusting–pustular dermatitis with acantholytic cells. The paw pad sample revealed crusting–pustular epidermitis with acantholytic cells, neutrophilic and eosinophilic exocytosis, and dermal edematous inflammatory cell infiltration. Results confirmed diagnosis of pemphigus foliaceus.