Exogenous Ochronosis Masquerading As Melasma in Skin of Color: Indications for Early Detection and Updated Clinical Review of Diagnosis, Pathomechanism, and Management.

Exogenous ochronosis (EO) is an uncommon but potentially disfiguring complication of prolonged topical hydroquinone use. It occurs most frequently in individuals with darker skin types and may clinically resemble melasma, often leading to delayed recognition and continued exposure to the offending agent. A 66-year-old female with Fitzpatrick skin type V presented with progressive facial hyperpigmentation, initially diagnosed as melasma and treated with repeated courses of topical hydroquinone. Despite therapy, pigmentation darkened over time, developing a slate-gray to blue-black discoloration. Reevaluation raised concern for EO based on clinical features and paradoxical worsening with continued treatment. Hydroquinone was discontinued, and the patient was treated with topical retinoids and strict photoprotection, resulting in stabilization of pigmentation at follow-up. Exogenous ochronosis remains an underrecognized diagnosis and a common source of iatrogenic progression when misclassified as treatment-resistant melasma. This case highlights a common diagnostic pitfall and provides clinical images and practical guidance for earlier recognition and management of EO in patients with skin of color.