Image Quiz: Dermatology—The case of the crusty cat
Both B and D are correct!
Cytologic examination of exudate under pinnal crusts reveals sterile inflammation with numerous large round acantholytic cells (arrow, Figure 2), and histologic examination of biopsy samples confirms pemphigus foliaceus. However, cytologic examination of the moist exudative crusts on the ventral trunk reveals septic suppurative inflammation due to a secondary bacterial infection (arrow, Figure 3) complicating the immune-mediated disease. A bacterial culture is indicated because of poor response to previous antibiotic therapy.
This case illustrates the importance of using both cytology and histology to obtain a complete diagnosis and to guide therapy. The cat responded well to immunosuppressive therapy with a combination of oral methylprednisolone and cyclosporine (Atopica—Novartis Animal Health), as well as a four-week course of oral antibiotics based on bacterial culture results. After six weeks of therapy, all crusting skin lesions were resolved (Figure 4), and immunosuppressive medications were slowly tapered over the next six months with no disease recurrence.
In most cases of pemphigus foliaceus, lifelong treatment is required. In this case, possible initiating stimuli for the pemphigus included an adverse drug reaction to previous medications or a paraneoplastic reaction to the recently excised thymoma.