A 25-year-old male presents with an itchy, erythematous, annular lesion with raised, scaly borders and central clearing on his left forearm. A KOH mount of skin scrapings from the active border would most likely reveal:

Explanation

The clinical description of an itchy, erythematous, annular lesion with raised, scaly borders and central clearing is classic for tinea corporis (ringworm), which is a dermatophyte infection. Dermatophytes are characterized by the presence of septate hyphae on a potassium hydroxide (KOH) mount of skin scrapings. Pseudohyphae and budding yeast cells are characteristic of Candida infections. Spores within hair shafts (endothrix) or around hair shafts (ectothrix) are seen in tinea capitis. Large, blunt-ended hyphae and spores (often described as 'spaghetti and meatballs' appearance) are characteristic of Malassezia furfur, the causative agent of pityriasis versicolor.