The Wood's lamp (365 nm UVA) examination in melasma shows enhanced contrast of pigmentation under the lamp compared to visible light. This 'Wood's lamp-accentuated' pattern indicates pigment is located in:

• A The dermis (dermal melasma)
• B Both the epidermis and dermis (mixed melasma)
• C The epidermis (epidermal melasma) ✓
• D The subcutaneous tissue

Explanation

Wood's lamp examination in melasma helps determine pigment depth. Epidermal melasma shows enhanced contrast (the lesion appears darker, more clearly demarcated) under Wood's lamp because UVA is absorbed by epidermal melanin. Dermal melasma shows no enhancement (contrast is lost/similar to visible light) because UVA does not differentiate dermal melanin well. Mixed melasma shows partial enhancement. This determination has therapeutic implications: epidermal melasma responds better to depigmenting agents (hydroquinone, kojic acid, retinoids), while dermal melasma is more refractory.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.