Key Takeaways
- Vitiligo shows chalk-/blue-white accentuation on Wood’s lamp with sharp borders and possible perifollicular islands.
- Scale, itch, or coppery/yellow fluorescence suggest tinea versicolor, not vitiligo.
- Ill-defined margins with fine scale favor pityriasis alba or post-inflammatory hypopigmentation.
- Confetti-like depigmentation at exposure sites raises suspicion for chemical leukoderma.
Quick Comparison Table
| Condition | Borders | Scale/Itch | Wood’s lamp | Dermoscopy/Notes |
|---|---|---|---|---|
| Vitiligo | Sharp; trichrome pattern possible | Minimal | Bright chalk/blue-white | Perifollicular islands; absent pigment network |
| Tinea versicolor | Variable, often ill-defined | Fine branny scale, mild itch | Yellow-gold/coppery accentuation | Scrape brings scale; KOH positive |
| Pityriasis alba | Ill-defined | Fine scale | Mild accentuation; low contrast | Pediatric cheeks common; improves with emollients |
| Post-inflammatory hypopigmentation | Ill-defined, matches prior rash | ± Scale (per cause) | Less bright than vitiligo | History of dermatitis/trauma; gradual repigmentation |
| Nevus depigmentosus | Stable, since early life | None | Off-white accentuation | Non-progressive; serrated borders |
| Chemical leukoderma | Confetti-like clusters | Possible irritant history | Confetti accentuation at contact areas | Phenol/paraphenylene exposure; remove trigger |
Wood’s Lamp Pearls
- Dark room, 365 nm, 3–5 min dark adaptation; lamp 5–10 cm from skin.
- Vitiligo: high-contrast blue-white glow; active rims may show confetti micro-macules.
- Tinea: uneven yellow-gold; seek scale at edges.
Dermoscopy Cues
- Vitiligo: absent network; perifollicular brown dots/halos (repigmentation islands).
- Pityriasis alba/tinea: superficial white scale; background erythema possible.
Point-of-Care Tests
- KOH prep for suspected tinea versicolor.
- Tape/scrape test to elicit fine scale (pityriasis alba/tinea).
- Biopsy rarely, for atypical or treatment-refractory cases.
Clinic Algorithm
- Pattern recognition (distribution, borders, symptoms) → Wood’s lamp.
- Scale/itch present? Do KOH or empiric antifungal trial if classic.
- No scale, sharp borders, chalk-white under lamp → manage as vitiligo; baseline photos and F-/T-VASI.
- Unclear cases → dermoscopy ± short follow-up or biopsy.