Abstract:

Exogenous ochronosis is an acquired dyschromia often induced by the chronic application of topical depigmenting agents containing hydroquinone. Three clinical stages of exogenous ochronosis have been described as erythema with mild hyperpigmentation, hyperpigmentation with pigmented colloid milium, and finally populo-nodular lesions with or without inflammation. The lesions are defined histopathologically by the pathognomonic finding of dermal sharply defined banana-shaped ocher-colored fibers. We report a case of exogenous ochronosis in a 74-year-old woman who presented with well-demarcated hyperpigmented plaques and papules of the upper back and left upper arm after years of topical application with 2% hydroquinone cream. Histopathologic examination of the biopsy revealed superficial and mid-dermal basophilic, thickened collagen bundles. This is the first case to document these findings in well-developed late-stage exogenous ochronosis. The absence of dermal banana-shaped ocher-colored fibers in this case may suggest this classic histopathologic finding may never develop and does not represent the terminal product of topical phenol application in a subset of patients. It is critical that pathologists are aware of the spectrum of histopathologic findings seen in exogenous ochronosis. This case underscores how poorly understood exogenous ochronosis pathogenesis remains, particularly how topically applied phenolic compounds interact with dermal extracellular matrix constituents.

Financial Disclosure:
No current or relevant financial relationships exist.

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Vanden Grube, BS