A 12-year-old boy presents with yellowish cup shaped crusts (scutula) matted onto the scalp with a musty odour, and patchy scarring alopecia. Direct microscopy shows air spaces within hair shafts. Which organism is the classical cause?
- A Trichophyton tonsurans
- B Microsporum gypseum
- C Trichophyton schoenleinii ✓
- D Epidermophyton floccosum
Correct answer: C. Trichophyton schoenleinii
Explanation
Favus is the distinctive form of tinea capitis classically caused by the anthropophilic endothrix fungus Trichophyton schoenleinii. Hyphae and air spaces grow within the hair shaft, and the pathognomonic scutulum is a yellowish cup shaped crust composed of debris and fungal elements around a single hair. Unlike ordinary tinea capitis, favus heals with permanent cicatricial alopecia. Microsporum gypseum is a geophilic ectothrix species, and Epidermophyton does not invade hair.
Reference: Rook's Textbook of Dermatology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.