Linear Porokeratosis Masquerading as Linear Epidermal Verrucous Nevus: A Case Report

Linear porokeratosis, a rare keratinization disorder, presents diagnostic challenges due to its clinical similarity to linear epidermal verrucous nevus and other linear dermatoses. We report a 10-year-old girl with pruritic, linear, hyperpigmented papules and plaques on the right forearm, progressing over 5 years with scarring from prior dermabrasion. Dermoscopy revealed a serpiginous double-edged keratin rim, collarette scales, follicular plugs, and a ring-in-ring appearance. At the same time, histopathology confirmed cornoid lamellae with parakeratotic columns, absent granular layer, dyskeratotic cells, and dermal melanophages. Treatment with topical tretinoin (0.05%) applied nightly achieved near-complete clearance within 4 months. This case underscores the critical role of dermoscopy and histopathology in distinguishing linear porokeratosis from mimics, ensuring accurate diagnosis. The efficacy of topical tretinoin in pediatric patients highlights the importance of tailored therapeutic approaches to prevent complications such as scarring or malignant transformation.