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Case Reports

Abstract

A 70-year-old man with a history of basal cell carcinoma, actinic keratoses, and seizures presented to his dermatologist with asymptomatic dark spots on his hands that may be exacerbated by trauma. The lesions had been intermittent for 5 years, with the most recent lesions atypically lasting over 6 months. A mucocutaneous exam revealed erythematous, violaceous, and brown coalescing macules and patches on the right dorsal hand. The clinical differential included solar lentigos and ecchymoses. A shave biopsy revealed macrophages throughout the dermis that contained intracytoplasmic dark brown pigment, which stained with both Fontana-Masson (melanin) and Perls’ (iron), consistent with drug-induced pigmentation. The patient’s prime drug suspect was phenytoin, a derivative of hydantoin that can stimulate melanocyte growth and proliferation. The patient’s other medications, lisinopril and sildenafil, are not associated with hyperpigmentation. Hydantoin-induced pigmentation classically presents as melasma-like brown patches symmetrically distributed on the face, and onset is usually within 2 years of hydantoin exposure. Uniquely, our patient may be only the second reported case involving the dorsal hands, and he had a delayed onset of 19 years. Clinicopathologic correlation is critical for diagnosis of drug reactions in atypical cases like this, and histologic data aids shared decision-making regarding management. Histologic findings of hydantoin-induced pigmentation include increased melanin in the stratum basale and/or dermis. While this pigmentation can fade within a few months to years after drug discontinuation, our patient and his neurologist elected to continue the phenytoin that had been controlling his seizures.