In lichen planus (LP), multiple studies have demonstrated that expression of PD-1 and PD-L1 is significantly reduced in lesional and nonlesional LP skin compared to healthy controls, suggesting that impaired PD-1/PD-L1 signaling may contribute to the loss of tolerance and the persistence of cytotoxic T cell-mediated inflammation characteristic of LP. The gene discussed is CD274; the disease is lichen planus.