Key Takeaways
- Wood’s lamp (365 nm) accentuates depigmented macules as bright blue-white/chalk-white with sharp rims.
- Dermoscopy helps confirm perifollicular islands, border activity, and early repigmentation patterns.
- A standardized photo protocol enables objective follow-up and F-VASI/T-VASI mapping.
- Differentiate from tinea versicolor, pityriasis alba, post-inflammatory hypopigmentation using lamp hues, scale, and dermoscopic clues.
Wood’s Lamp Criteria
- Color/Contrast: Vitiligo lesions appear chalk-white/blue-white, high contrast vs surrounding skin.
- Borders: Usually sharp; active lesions may show confetti-like micro-macules at the rim.
- Patterns: Trichrome (normal → hypopigmented → depigmented), marginal hyperpigmentation, perifollicular islands indicating repigmentation potential.
- Sites: Face/neck show earliest islands; acral sites display fragmented rims.
- Technique: Dark room, allow 3–5 min dark adaptation; hold lamp 5–10 cm from skin; shield external light sources.
Dermoscopy Findings
- Perifollicular repigmentation: brown dots/halos around follicles coalescing centripetally.
- Border activity: scattered tiny depigmented confetti at advancing edges.
- Pigment network: attenuated/absent within macule; re-emergence indicates response.
- Scale/vessels: typically minimal/absent in vitiligo; scale favors tinea/pityriasis alba.
Differential Diagnosis & Pitfalls
| Condition | Wood’s lamp | Dermoscopy/Clinical | Tip |
|---|---|---|---|
| Vitiligo | Bright blue-white; sharp rims; trichrome possible | Perifollicular islands; minimal scale | Map for F-VASI |
| Tinea versicolor | Yellow-gold/coppery accentuation (variable) | Fine branny scale; KOH positive | Scrape test reveals scale |
| Pityriasis alba | Mild accentuation; low contrast | Fine scale; ill-defined edges | Peds cheeks common |
| Post-inflammatory hypopigmentation | Less bright; ill-defined | Background dermatitis history | Improves over months |
| Chemical leukoderma | Confetti-like depigmentation at exposure sites | History of irritant/phenols | Remove trigger |
Standardized Photo Protocol
- Consent & privacy: document informed consent; de-identify images.
- Setup: blackout room; diffuse ambient off; Wood’s lamp 365 nm; tripod-mounted camera/smartphone.
- Camera: fixed distance (e.g., 1.0 m for face), perpendicular angle; RAW if available; fixed ISO/shutter/white balance; include scale marker or anatomical landmarks.
- Series: daylight photos + Wood’s lamp photos at baseline and follow-ups; keep identical framing.
- Notes: mark sites on a body diagram; record phototype, prior treatments, and session numbers.
Mapping & Follow-Up
- Use standardized photos to compute F-VASI/T-VASI and track perifollicular islands emergence.
- Document border contraction and trichrome evolution; high-risk zones may need maintenance topicals or light.
- Flag Koebner sites (friction/trauma) for counseling and barrier care.
Limitations
Wood’s lamp hues vary by device and ambient control; dermoscopy is operator-dependent; coexisting dermatoses may confound interpretation—correlate with history and, if needed, mycology or biopsy.