A 22-year-old man presents with multiple well-demarcated hypopigmented macules over his chest and back with fine scaling, more noticeable after sun exposure. KOH mount of the scrapings shows round budding yeasts with short curved hyphae. The organism fails to grow on routine Sabouraud agar unless olive oil is overlaid on the medium. The causative agent is:

• A Candida glabrata
• B Malassezia furfur ✓
• C Trichosporon asahii
• D Hortaea werneckii

Explanation

Pityriasis (tinea) versicolor is caused by Malassezia furfur, whose KOH picture of yeasts plus short hyphae is classically described as 'spaghetti and meatballs'. The organism is a lipophilic yeast and requires long-chain fatty acids for growth, hence the need for oil-supplemented media such as Dixon agar or olive oil overlay on Sabouraud agar. Trichosporon causes white piedra, and Hortaea werneckii causes tinea nigra, neither of which shows hypopigmented scaling macules.

Reference: Jawetz, Melnick and Adelberg's Medical Microbiology, 28th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.