Mechanisms Underlying Lichen Planus in Association with Biologic Therapy.

Cutaneous reactions, including lichen planus (LP) and related lichenoid eruptions have been increasingly reported in association with biologic therapies including immune checkpoint inhibitors and tumor necrosis factor-α inhibitors. Since the immunologic mechanisms underlying biologic-associated LP remain unclear, we aimed to summarize current evidence on biologic-induced LP, outline implicated drug classes, and propose mechanistic models. We conducted a comprehensive systematic analysis of PubMed literature, reviewing 145 publications that identified 157 cases of biologic-associated LP and proposed several overlapping immunological mechanisms, including cytokine imbalances, T cell immune pathway shifts, antigen unmasking, keratinocyte apoptosis dysregulation, and host susceptibility. Management of biologic-associate LP includes withdrawal of the offending biologic and adjunctive treatment. Further research is needed to clarify mechanistic pathways, define incidence, and identify predictive biomarkers that may guide risk stratification.