Abstract: A 6-year-old girl presented with a light erythema on her right cheek with no scales or pustules. Under dermoscopy, the diseased hair was found to be shortened with a few scales on the root. By fluorescent staining, the diseased hair was surrounded by transparent hyphae which emitted bright blue fluorescence, and the hyphae grew along the direction of the hair shaft, some of which were extended to the surroundings. No hyphae or spores were found in the dandruff under the dermoscopy. The pathogen was identified by morphology and molecular biology as Athroderma otae (teleomorph of Microsporum canis). The diagnosis of tinea of vellus hair on a child’s face was made. Oral itraconazole capsule 100 mg/d and topical terbinafine cream were administrated. After 4 weeks’ follow-up, the child’s facial background color returned to normal, and microscopic examination showed negative result, so the medications were stopped. There was no recurrence in 3 months’ follow-up.

Key words: tinea of vellus hair, dermoscopy, indistinguishable tinea