Lichen planus

Lichen planus (LP) is the prototypical lichenoid tissue reaction (LTR) that affects approximately 1 % of the population worldwide. Classic LP is characterized by violaceous, flattopped, polygonal papules, which favor the flexor aspects of the body. LP can affect any ectodermally derived tissues (skin, hair, nail, mucous membranes, esophagus) and therefore a complete physical examination and multidisciplinary approach is often needed. Histologically, LP is characterized by basal keratinocyte damage with a brisk LTR. While there is a clear genetic association with LP, the pathogenesis remains unknown. Antigen presenting cells and T-lymphocytes play a key role in antigen recognition, lymphocyte activation, keratinocyte apoptosis, and disease resolution. Numerous therapeutic modalities have been utilitzed in LP. We recommend the usage of anti-inflammatory agents, which specifically target T-lymphocytes. Future, novel therapeutic targeting of cytotoxic T-lymphocytes make mechanistic sense; although, future studies are needed for both clinical efficacy and safety.