Lichen planus, the prototype of lichenoid dermatoses, is an idiopathic, T cell-mediated, autoimmune, inflammatory disease. It may affect the skin, hair, nails, and mucous membranes. Many clinical variants of lichen planus have been described, including lichenoid drug eruption or drug induced lichen planus, associated with a myriad of culprit medications. We describe a 63-year-old woman with longstanding psoriasis effectively controlled with ixekizumab, who developed lichenoid drug eruption. Her lichen planus lesions improved after treatment discontinuation and the patient was started on an IL23 inhibitor to treat her psoriasis through an alternative mechanism of action. Our report adds to the literature and provides insight into the complex pathophysiology of lichen planus.
