Tinea corporis due to Microsporum canis from an asymptomatic dog.

The patient was a 19-year-old female student who purchased a puppy from a pet shop four weeks earlier. At the time of her first examination, an annular edematous erythema with adherent scales and vesicles surrounding its margin was seen on the left forearm. On direct examination of the vesicles, fungal elements were detected, and Microsporum canis was isolated. The puppy was a Pomeranian and was kept in the house at all times. No clinical lesions were seen on the puppy, and the Wood's lamp test was negative. However, M. canis was isolated from the animal by the hairbrush method. Symptoms disappeared after the patient was treated topically with terbinafine cream for three weeks. Although the dog received no treatment whatsoever, there was no evidence of the disease on the pet. Results of the hairbrush method performed on the pet two and three weeks later were negative, but, at five weeks, it was again positive. Human infection with M. canis from an asymptomatic dog was demonstrated in this case. Attention should be paid to preventing infections from animals without lesions.