Tinea Versicolor (Pityriasis Versicolor)
Tinea versicolor is the skin mycosis that shows faint yellow (yellow-green) fluorescence under Wood's lamp (UV light). 1
Key Fluorescence Characteristics
The yellow-green fluorescence of tinea versicolor is caused by the Malassezia species (formerly Pityrosporum) that causes this superficial fungal infection. This distinctive fluorescence pattern helps differentiate it from other skin conditions 1.
Important Distinction: Favus Also Fluoresces
While tinea versicolor is the most common mycosis showing yellow fluorescence, favus (a chronic inflammatory tinea capitis caused by Trichophyton schoenleinii) also fluoresces under Wood's lamp 2. However, favus presents very differently clinically—with yellow, crusted, cup-shaped lesions called "scutula" on the scalp, primarily seen in the Middle East and North Africa, and can cause scarring alopecia 2.
Clinical Context
Wood's lamp examination serves as a rapid, non-invasive screening tool for fungal infections:
- Tinea versicolor: Yellow-green fluorescence on trunk/upper body patches
- Favus: Fluorescence on scalp with characteristic scutula formation
- Microsporum canis tinea capitis: Bright green-blue fluorescence (not faint yellow)
Common Pitfall to Avoid
Do not confuse tinea versicolor with erythrasma, which shows coral-red fluorescence (not yellow) under Wood's lamp and is caused by Corynebacterium minutissimum bacteria, not a fungus 3. This distinction is critical as treatment differs—antifungals for tinea versicolor versus antibiotics for erythrasma.
Ultraviolet-induced fluorescence dermoscopy has demonstrated 98.63% sensitivity for detecting cutaneous fungal infections 4, making it a highly reliable adjunctive diagnostic tool when combined with KOH preparation for confirmation.