Hydroquinone-induced exogenous ochronosis: a report of four cases and usefulness of dermoscopy.

Hydroquinone is the first choice of topical bleaching agents used in treatment of melasma. In Brazil, hydroquinone is widely prescribed by physicians and often used by patients without a prescription. The principal adverse effects of its chronic use are confetti-like depigmentation and exogenous ochronosis. The latter manifests clinically with gray-brown or blue-black hyperpigmentation, as well as pinpoint hyperchromic papules that look like caviar, and therefore called caviar-like. On histopathology, curved ochre-colored structures, 'banana-shaped' fibers, appear in the papillary dermis. No description of dermoscopy in ochronosis is found in the literature. We report four cases of hydroquinone-induced exogenous ochronosis. Dermoscopy was performed in two patients on the areas with ochronosis, and in addition to the melasma findings, amorphous densely pigmented structures obliterating some follicular openings were observed. Exogenous ochronosis is an avoidable dermatosis that is difficult to treat. Dermatologists should be able to differentiate it from melasma and immediately discontinue hydroquinone. Dermoscopy might become a valuable resource in approaching exogenous ochronosis.