Image Quiz
A 4-year-old spayed English bulldog presented with acute onset skin lesions. Her owners had just traveled across the state, and several days after returning home, noticed red bumps on her skin. She was not reported to be pruritic, but her skin lesions rapidly worsened.
On physical examination the dog was quiet, alert, and responsive with a rectal temperature of 102.5 °F. Her skin was painful to the touch. Clinical pictures of her skin lesions are shown in Figures 1, 2, and 3. Cytology of an intact pustule is shown in Figure 4.
Based on this information, what differential should you consider?
A: Allergies
B: Pemphigus foliaceus
C: Cutaneous lupus erythematosus
D: Superficial staphylococcal folliculitis
(find the answer at the end of the article!)
This dog’s history, clinical picture, and cytologic findings were consistent with the subcorneal pustular disease pemphigus foliaceus (PF). Additional differentials to consider included cutaneous adverse drug reaction, severe staphylococcal folliculitis and furunculosis, and acantholytic dermatophytosis.1
PF is the most common autoimmune blistering disease in dogs.2 A cytologic hallmark of PF is inflammation characterized by acantholytic keratinocytes (the large purple cells shown on Figure 4) admixed with neutrophils, with or without eosinophils. This acantholysis occurs because of the production of autoantibodies targeting desmocollin 1 in the desmosome, the glue that holds the keratinocytes together.2,3
“PF may occur spontaneously in dogs of any age and with no known trigger. It is also possible that the development of PF may be due to an adverse cutaneous drug reaction therefore a thorough drug history is always warranted. In this patient, the recent travel may have been a stressful trigger that induced her PF.”
On dermatologic examination, this dog had numerous pustules with severe secondary crusting affecting her face, pinnae, paw pads, dorsum, ventrum, and limbs. An excellent differential for a pustular crusting disease is staphylococcal folliculitis. Staphylococcal infections, however, rarely affect several select locations on the dog such as the face, pinnae, and paw pads. When pustular crusted lesions are observed in these locations, an autoimmune disease such as PF should be prioritized as a differential. The definitive diagnosis of PF should be made with skin biopsies and histopathology because treatment involves long-term immunosuppression.4
Including intact pustules and crusts in the biopsy samples is crucial because PF cases often have few to no changes in the dermis.5 Biopsies taken of this dog confirmed the clinical suspicion of pemphigus foliaceus.
Glucocorticoids at immunosuppressive doses, accompanied by a concurrent immunosuppressive therapy (cyclosporine, azathioprine, mycophenolate, doxycycline/ niacinamide, or chlorambucil) are typically recommended for treatment.4 Spontaneous PF will likely need to be treated for the life of the pet, which is why glucocorticoids as sole therapeutics are not recommended in dogs. No 2 patients respond the same to treatment, so trial and error may be required to establish the most suitable immunosuppressive protocol for that individual.
For this patient, treatment was initiated with dexamethasone (0.2mg/kg orally, once daily) and mycophenolate (12.5mg/kg orally, twice daily) for immuno- suppression and doxycycline (5mg/kg twice daily) based on culture and susceptibility for the secondary infection. Significant clinical improvement occurred in the month following treatment initiation, and the dexamethasone was gradually tapered until remission was maintained with twice-daily mycophenolate and twice-weekly dexamethasone at 0.03 mg/kg.
Julia E. Miller, DVM, DACVD, is a specialist at the Animal Dermatology Clinic in Louisville, Kentucky. She has a special interest in treating difficult otitis externa and large animal dermatology.
Image Quiz answer: B, Pemphigus foliaceus
References
- Parker WM, Yager JA. Trichophytondermatophytosis--a disease easily confused with pemphigus erythematosus. CanVet J.1997;38(8):502-505.
- Olivry T. A review of autoimmune skin diseases in domestic animals: I –superficial pemphigus. Vet Dermatol.2006;17(5):291-305.doi:10.1111/j.1365-3164.2006.00540.x
- Bizikova P, Dean GA, Hashimoto T, Olivry T. Cloning and establishment of canine desmocollin-1 as a major autoantigen in canine pemphigus foliaceus.Vet Immunol Immunopathol.2012;149(3-4):197-207.doi:10.1016/j.vetimm.2012.06.025
- Miller WH, Griffin CE, Campbell KL. Autoimmune and immune-mediated dermatoses.In: Muller and Kirk‘s Small Animal Dermatology.7th ed. W.B. Saunders;2013:432-445.
- Gross TL, Ihrke PJ, Walder EJ, Affolter V. Pustular diseases of the epidermis.In: Gross TL, Ihrke PJ, Walder EJ, Affolter V. Skin Diseases of the Dog and Cat:Clinical and Histopathologic Diagnosis. 2nd ed. Blackwell Publishing;2005:13-18.
