Pigmented Actinic Lichen Planus Mimicking Chronic Photodermatitis in a Fair-Skinned Caucasian Woman: A Case Report.

Abstract

Actinic lichen planus (ALP) is a rare photosensitive variant of lichen planus that typically affects young individuals with dark skin phototypes living in tropical and subtropical regions. Reports in fair-skinned Caucasian patients are exceptional, often making the diagnosis challenging. We describe the case of a 52-year-old Caucasian woman with Fitzpatrick skin phototype II who presented with a 2-year history of recurrent erythematous-violaceous reticulated plaques involving the lateral aspects of the neck. The lesions showed seasonal exacerbation following sun exposure and had initially been misdiagnosed as chronic photodermatitis. Dermoscopy revealed Wickham striae and gray peppering, suggestive of a lichenoid dermatosis. Histopathologic examination demonstrated a lichenoid interface dermatitis with basal vacuolar degeneration, cytoid bodies, compact hyperorthokeratosis, and marked pigment incontinence, confirming the diagnosis of pigmented actinic lichen planus. The patient was treated with topical clobetasol followed by tacrolimus, adapalene, and strict photoprotection, resulting in disease stabilization and partial improvement at 6-month follow-up. This case expands the clinical spectrum of ALP by documenting its occurrence in a fair-skinned Caucasian woman and highlights the importance of integrating clinical, dermoscopic, and histopathologic findings to establish the correct diagnosis in atypical presentations.