Atypical and Polymorphic Presentation of Lichen Planus in a 16-Year-Old Boy: A Rare and Intriguing Case.

Lichen planus (LP) is an inflammatory condition of the skin characterized clinically by purple, polygonal, pruritic papules and histopathologically by lymphocytic infiltrate at the dermoepidermal junction. Atypical hypertrophic, atrophic, and annular forms have also been described in the literature. We report a rare case of polymorphic LP in a 16-year-old male with a 10-year history of mildly pruritic, hyperpigmented lesions involving the trunk, extremities, genitalia, and scrotum. Clinical examination revealed a mix of classical LP papules, verrucous/rupoid plaques, annular porokeratosis-like lesions, and areas of erosion. Dermoscopy showed Wickham's striae; histopathology demonstrated a lichenoid lymphocytic infiltrate, saw-tooth acanthosis, wedge-shaped hypergranulosis, colloid bodies, and compact orthohyperkeratosis, confirming LP. The patient responded well to a short systemic steroid taper combined with a topical potent corticosteroid (mometasone) and keratolytic therapy. This case highlights the diagnostic challenge of polymorphic LP in adolescents and underscores the value of dermoscopy and histology in atypical presentations.