Pigmented actinic lichen planus: a case report.

Abstract

Actinic lichen planus (ALP) is a rare photosensitive subtype of lichen planus (LP) with four major forms recognized: annular, pigmented (melasma-like), dyschromic, and classic lichenoid. The prevalence is highest among dark-skinned younger females residing in tropical and subtropical regions. There are very few reports of ALP across Europe, with most of the cases among individuals living in warm countries or in people of Middle Eastern and Indian ancestry. We report a case of a 68-year-old white man that presented with a 9-year history of a mildly pruritic solitary hyperpigmented patch on the tip of his nose. Histopathological examination demonstrated signs of classic LP with epidermal atrophy, pigmentary incontinence, and signs of solar elastosis. Based on these findings, a diagnosis of pigmented ALP was established. Topical pimecrolimus and tretinoin along with rigorous photoprotection proved effective, with mild residual hyperpigmentation after 6 months of treatment. Many differential diagnostic possibilities should be considered for such a lesion. Nevertheless, a biopsy and correlation of histopathological and clinical findings can shorten the time from onset to a proper diagnosis. Treating both the hyperpigmented and inflammatory component of this dermatosis is necessary, as well as strict long-term photoprotection to prevent recurrences.