What are the causes of Lichen Planus?
The exact cause of Lichen planus is not known. The pathogenesis of LP is immunologically mediated. Whether the foreign antigen is a virus or a drug is not known. Langerhans cells process antigens, which are then presented to T lymphocytes. This stimulated lymphocytic infiltrate is epidermotropic and attacks keratinocytes. During this lymphocytotoxic process, the keratinocytes release cytokines that attract more lymphocytes. This process has been referred to as the lichenoid tissue reaction. In addition, recent studies reveal a disruption in the epithelial anchoring system. Some drugs, such as those containing arsenic, bismuth, or gold can cause a reaction that is indistinguishable from the rash of lichen planus. Exposure to certain chemicals used in the development of color photographs can also produce a similar rash. The long-term use of the drugs quinacrine or quinidine (used for malaria, certain microscopic organisms, and worms) may produce hypertrophic lichen planus of the lower le
