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Abstract
Lichen Planus (LP) is a condition in which autoreactive T lymphocytes attack basal keratinocytes in the skin, mucous membranes, hair follicles, and/or nail units. Lesions are classically described using the 6 Ps (purple, planar, polygonal, pruritic, papules, and plaques), but some lesions develop fine, grayish-white streaks called Wickham’s striae. There are also several variations of LP including hypertrophic, follicular, ulcerative, annular, and linear. We report a case of a 60-year-old male who presented with a worsening rash on the left upper back that had been present for months. The rash started as individual red papules that darkened and coalesced into violaceous plaques in a linear distribution. He noted occasional pruritus but no oral lesions, joint pains, or nail changes. Linear LP can imitate many other skin conditions including psoriasis, subacute cutaneous lupus erythematosus, lichen striatus, inflammatory linear verrucous epidermal nevus, and mycosis fungoides. Distinguishing LP from other skin conditions is important in guiding management, and healthcare providers should perform a thorough oral mucosa examination if LP is suspected. While cutaneous LP will typically spontaneously resolve within 1-2 years, severe or persistent oral LP needs to be carefully followed as these patients are at higher risk for oral squamous cell carcinoma.