A woman using hydroquinone 4% cream continuously for 2 years develops blue-black pigmentation over her cheeks that does not lighten with sun protection. Histology shows ochre-coloured granules in the dermis. What is the diagnosis?
- A Dermal melasma
- B Exogenous ochronosis ✓
- C Lichen planus pigmentosus
- D Drug-induced pigmentation from minocycline
Correct answer: B. Exogenous ochronosis
Explanation
Prolonged continuous use of hydroquinone, especially above 2% strength and without cyclical breaks, causes exogenous ochronosis: blue-black pigmentation due to homogentisic acid-derived ochronotic granules deposited in the dermis. Dermal melasma would have been present before treatment, lichen planus pigmentosus shows interface change, and minocycline pigmentation requires a drug history rather than a bleaching cream.
Reference: Fitzpatrick's Dermatology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.