Crusting in a Geriatric Cat
Sammie (17 MN DSH) has a three-week history of lethargy, anorexia, along with exudate and crusting of both ears, not responsive to topical otic therapy (gentamicin-clotrimazole-betamethasone). The lesions progressed over the past 5 days to involve crusting and pruritus around the chin and rostral muzzle. He has no previous history of skin issues or pruritus. There were no medications or vaccinations administered within 6 months of disease onset.
Andrew Simpson, DVM, MS, DACVD
VCA Aurora Animal Hospital, Aurora IL
T: 104.1 F
P: 120 bpm
R: 36 bpm
mm: pink, moist
CRT: 1-2 seconds
On general physical examination the following were noted: heart and lungs auscult clearly in all fields, lymph nodes palpate normally, abdomen is soft and non-painful; normal oral examination. Otoscopic examination showed no inflammation or debris within the canals (only involved the pinnae), the tympanic membrane was normal in appearance bilaterally.
Dermatologic examination revealed severe crusting and purulent exudate involving the medial aspects of both pinnae (Figure 1) in addition to severe crusting and mild hemorrhage of the ventral chin and areas around the maxillary lip fold/vibrissae region (Figure 2). Mild crusting involved the nasal planum.
Figure 1. Severe crusting and purulent exudate on the margin and medial aspects of the pinna in a cat with pemphigus foliaceus.
Figure 2. Crusting and alopecia involving the ventral chin and rostral muzzle. Mild crusting of the nasal planum is also present.
Differential diagnoses consisted of dermatophytosis, allergic dermatitis +/- bacterial pyoderma, pemphigus foliaceus, cutaneous lymphoma, and cutaneous lupus.
Skin cytology revealed numerous neutrophils along with acantholytic keratinocytes (Figure 3). No infectious organisms were noted.
Figure 3. Acantholytic keratinocytes among a group of neutrophils from a stained impression smear of erosive, crusted skin on a cat with pemphigus foliaceus.
A complete blood cell count, serum biochemistry, urinalysis and total thyroid hormone assay were all within normal limits.
Differential diagnoses after finding acantholytic keratinocytes included pemphigus foliaceus, superficial bacterial pyoderma and dermatophytosis. In cats, pyoderma and dermatophytosis are less likely causes for acantholysis, but a skin biopsy was recommended.
Sammie was placed under general anesthesia in order to obtain biopsies of the skin from the base of the pinna as well as the ventral chin. Fungal culture showed no dermatophyte growth. Aerobic culture of the skin showed no growth of bacterial organisms. Histopathology revealed subcorneal pustules with acantholytic keratinocytes. A definitive diagnosis of pemphigus foliaceus was made based on these results.