A 55-year-old woman develops paradoxical skin darkening after using a hydroquinone-based cream for melasma. Explore the diagnosis and management.
A 55-year-old woman presented to the dermatology clinic with a 1-year history of skin darkening on her face. Two years before presentation, she had started applying a skin-lightening cream containing hydroquinone to her face daily to treat melasma. On physical examination, bluish-brown patches with background erythema and telangiectasias were observed on the cheeks, nasal bridge, and perioral region, with lesser involvement on the forehead (left). Dermoscopy of the affected areas revealed hyperchromic, pinpoint macules (middle). A skin-biopsy sample from the left cheek showed extracellular deposition of yellow-brown, banana-shaped bodies in the dermis (right, hematoxylin and eosin stain). What is the most likely diagnosis?
