Dermatophytosis Caused by Trichophyton rubrum Infection in a Dog

A 7-year-old castrated male Yorkshire terrier was presented with a 1-year history of pruritic skin lesions on the face and right thigh. On presentation, the dog had scale and crust around the eyes, muzzle and nasal planum, and scaling alopecia with papules extending from the hip to the right thigh. The advancing edge was characterized by an erythematous border. Skin cytology revealed non-degenerate neutrophils, macrophages and acantholytic cells. Skin scrapings indicated fungal hyphae in the scale. Histopathological examination revealed lymphocyte infiltration into the epidermis and follicular wall, and interface dermatitis with liquefaction. Periodic acid-Schiff-positive hyphae were detected within the stratum corneum. Fungal cultures and DNA sequencing analysis identified Trichophyton rubrum, and the dog was diagnosed with dermatophytosis caused by T. rubrum infection.