A 25-year-old man has multiple discrete, soft, white nodules firmly attached along the shafts of his pubic hairs. The hairs do not break easily, there is no fluorescence on Wood's lamp examination, and KOH of a plucked hair shows hyphae and arthrospores surrounding the shaft. What is the most likely causative organism?
- A Piedraia hortae
- B Trichosporon asahii ✓
- C Corynebacterium tenuis
- D Microsporum canis
Correct answer: B. Trichosporon asahii
Explanation
White piedra is caused by Trichosporon species, most commonly Trichosporon asahii, and presents as soft white to light brown nodules on axillary, pubic or facial hair composed of hyphae and arthrospores arranged sheath-like around the shaft. Black piedra, caused by Piedraia hortae, forms hard, gritty black nodules mainly on scalp hair. Corynebacterium tenuis causes trichomycosis axillaris, which gives yellow concretions rather than true fungal nodules.
Reference: Fitzpatrick's Dermatology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.