Cytologic diagnosis of generalized cutaneous sporotrichosis in a hunting hound.

A 1-year-old male Foxhound/Walker Hound mix was presented to the small animal internal medicine service at Louisiana State University School of Veterinary Medicine with a 6-week history of progressive, multifocal, ulcerative and draining, well-circumscribed lesions in a generalized distribution. Prior to referral, a presumptive diagnosis was made of sterile pyogranulomatous disease; immunosuppressive therapy was instituted but resulted in clinical deterioration. At presentation, the dog had marked neutropenia (1100 neutrophils/microL), and a mild toxic left shift (400 bands/microL). Cytologic findings in the exudates from a draining skin lesion included high numbers of markedly degenerate neutrophils (about 95% of nucleated cells) as well as low numbers of macrophages, small mature lymphocytes, and eosinophils. Low numbers of intracellular (within neutrophils and macrophages) and extracellular, pleomorphic, cigar-to-ovoid shaped organisms ( approximately 3x9 microm) consistent with Sporothrix were observed. Histopathologic examination of a skin biopsy showed marked, chronic, active, ulcerative, pyogranulomatous dermatitis and panniculitis, with intralesional yeast consistent with Sporothrix sp. The etiologic agent was confirmed as Sporothrix schenckii by macerated tissue fungal culture. The patient was treated with itraconazole, enrofloxacin, and clindamycin, with clinical resolution occurring over a 3-month period. This case is a rare example of the cytologic diagnosis of Sporothrix schenckii in a canine patient. Diagnosis of canine sporotrichosis is often challenging and usually requires tissue culture, as infected dogs typically harbor very few organisms. The patient's prior immunosuppressive therapy likely contributed to higher numbers of organisms in exudates from the cutaneous lesions, facilitating cytologic diagnosis.