Pemphigus foliaceus: Chronic cases typical, challenging to treat
As the years go by, I am amazed by the number of difficult cases that I continue to see in my practice.
The following case is a patient that made me work hard to come to a definite diagnosis, but who responded modestly to appropriate medical therapy.
A 4-year-old spayed female Cattle Dog presented with a three- to four-month history of alopecia, crusts and some loss of pigment on the nose. The owner reported that the dog rubbed the muzzle a fair amount, and that blood was seen on the rug where the dog rubbed its nose. In addition, the owner was told by her primary veterinarian to keep the dog away from sunlight between 10 a.m. and 4 p.m., since this was most likely exacerbating the lesions. The referring veterinarian recommended sunblock applied to the affected area every 12 hours and prescribed topical triamcinolone cream and 500 mg niacinamide every eight hours as well as 500 mg tetracycline every eight hours.The owner felt the lesions did not respond to treatment (the dog licked off most of the topical products after application), and seemed to get worse over time.
The physical examination revealed patches of depigmentation on the planum near the nares opening as well as the alar folds in a symmetrical pattern (Photo 1). Alopecia was noted on the dorsal muzzle (haired area near the planum) and was accompanied by focal crusts and erosions, and one large pustule (Photo 2). A higher magnification of the pustule is seen in Photo 3.
Differential diagnoses for these lesions included pemphigus foliaceus, pemphigus erythematosus, superficial bacterial folliculitis, discoid lupus erythematosus, drug eruption, pustular dermatophytosis, T-cell lymphoma and Vogt-Koyanagi-Harada-like syndrome.
My initial diagnostic plan included cytology of the pustule. A skin biopsy of the crusts and pustule was performed with local analgesia in combination with intravenous medetomidine/butorphanol. The results revealed numerous intact, non-degenerate neutrophils; few eosinophils; and numerous acantholytic cells (rounded keratinocytes). These findings were compatible with pemphigus foliaceus as described in the dog.
The results of skin histopathology revealed broad, superficial, subcorneal pustules containing varying degrees of acantholytic cells (normal epidermal kertinocytes that have lost their cohesion). Some of the pustules extended into the follicular epithelium. All the pustules contained numerous neutrophils and few eosinophils. Some dermal inflammation was noted just below the basement zone.
The combination of the clinical presentation, results of cytology, and the results of skin histopathology proved diagnostic for facial pemphigus foliaceus.
Clinical remission was not achieved with the combination of prednisone and azathioprine. Cyclosporine alone and oral triamcinolone also failed to reduce the pustule formation. The case was lost to follow-up.