At presentation to the dermatology service, the patient was in good general health aside from its left front leg lameness
and extensive skin lesions. The dermatologic examination revealed a 30-x-30-cm area of crusting in the interscapular region
that extended down the shoulder blades (Figures 1A & 1B). Crusts were also evident on the concave aspects of both pinnae (Figure 1C), and hyperkeratosis was noted on the footpads on the left front foot, possibly suggesting previous epithelial damage.
Cytologic examination of purulent exudate obtained from a crusted lesion on the shoulder revealed neutrophils and acantholytic
keratinocytes suggestive of pemphigus foliaceus. The original biopsy samples were requested for review. Serum was collected
for detection of circulating antikeratinocyte autoantibody by indirect immunofluorescence in the NCSU laboratory.
Figure 1A-1C. The patient in Case #1 at presentation: 1A) The lesions at the ProMeris application site (the area is partially
shaved). 1B) A close-up of this region reveals severe crusting, mild erythema, and shallow erosions underneath these crusts.
1C) In addition to lesions at the preventive application site, crusts, mild erythema, and scaling were discovered on the concave
aspects of the pinnae.
Diagnosis and treatment
Pending the histologic examination and immunologic testing results, and based on the strong suspicion of ProMeris-triggered
pemphigus foliaceus, the glucocorticoid was changed to prednisolone, and the dose was increased to 1.5 mg/kg twice daily,
while tramadol was to be given as needed to relieve pain.
The results of the histologic examination confirmed the presence of superficial epidermal neutrophilic pustular dermatitis
with keratinocyte acantholysis. Bacteria or dermatophytes in the stratum corneum were not seen by using special stains. Direct
immunofluorescence performed on paraffin-embedded skin sections revealed intercellular deposits of IgG and IgM in lesional
and perilesional epidermis. Circulating antikeratinocyte autoantibodies were not detected at a 1:20 serum dilution.
All together, the dog's history, clinical signs, and results of cytologic and histologic examinations and direct immunofluorescence
testing were highly suggestive of a diagnosis of ProMeris-triggered pemphigus foliaceus.
The dog returned for a reevaluation the next week. The skin lesions had markedly improved—only minor crusting was present
in the interscapular region and pinnae. The dog no longer exhibited signs of lameness, and the tramadol was discontinued.
The prednisolone dose was tapered over the next 11 days, and the disease has remained in remission without any relapse for
more than two years. The dog subsequently began to receive Frontline Plus (Merial) as a topical flea and tick preventive.
This product was well-tolerated, and no recurrence of the skin lesions was reported by the owner.