In melasma, which of the following dermal changes distinguishes the dermal type from the epidermal type on Wood's lamp examination?
- A Dermal melasma shows no enhancement — the contrast between affected and normal skin is similar under Wood's lamp as under visible light ✓
- B Dermal melasma shows enhancement (brighter contrast) under Wood's lamp
- C Dermal melasma fluoresces bright white, similar to depigmented vitiligo patches
- D Dermal melasma shows coral red fluorescence due to porphyrin production
Correct answer: A. Dermal melasma shows no enhancement — the contrast between affected and normal skin is similar under Wood's lamp as under visible light
Explanation
Wood's lamp (365 nm UVA) helps classify melasma: epidermal type shows enhanced contrast (the hyperpigmented areas appear darker/more defined under Wood's lamp) because melanin in the epidermis absorbs more UV light. Dermal melasma does NOT show enhancement under Wood's lamp because deep melanin in dermal macrophages does not affect the Wood's lamp contrast differentially. The mixed type shows variable enhancement. Epidermal melasma responds better to topical depigmenting agents.
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.