Lichen Planus and Lichenoid Dermatoses

Lichen planus (LP) is an uncommon inflammatory and intensely pruritic disorder that can affect the skin, nails, or mucous membranes. Its pathogenesis is not fully understood but is considered a T-cell-mediated autoimmune disease. Cutaneous lesions appear as violaceus, polygonal, papules, or plaques with a predilection for the wrists, ankles, and lower back. The oral variant, oral lichen planus, can present in two main forms, the reticular form and, less frequently, the erosive form, usually bilaterally and symmetrically. LP is a model for lichenoid dermatoses, a group of inflammatory skin conditions that share similar clinical presentations and histopathological findings. In addition to lichen planus, this group includes lichenoid drug eruption, lichen sclerosus, lichen nitidus, and lichen striatus.