- Lichen Planus is an rare, recurrent, inflammatory condition of the skin and mucous membranes with unknown origin characterized by shiny reddish-purple spots on the skin and gray-white ones in the mouth.
- “Pruritic, purple, polygonal, planar papules, and plaques” are the tongue-twisting Ps that describe this disorder of skin and squamous mucosa.
- The lesions may result from a CD8+ T cell–mediated cytotoxic immune response against antigens in the basal cell layer and the dermoepidermal junction that are produced by unknown mechanisms, perhaps as a consequence of a viral infection or drug exposure.
- The cause is unknown, but it is thought to be the result of an autoimmune process with an unknown initial trigger.
- Cutaneous lesions of lichen planus consist of pruritic, violaceous, flat-topped papules, which may coalesce focally to form plaques. These papules are often highlighted by white dots or lines called Wickham striae.
- Hyperpigmentation may result from melanin loss into the dermis from damaged keratinocytes.
- Microscopically, lichen planus is a prototypical interface dermatitis, so called because the lesions are concentrated at the interface of the squamous epithelium and papillary dermis. There is a dense,
continuous infiltrate of lymphocytes along the dermoepidermal junction.
- The lymphocytes are intimately associated with basal keratinocytes, which often atrophy or become necrotic.
- Perhaps as a response to damage, the basal cells take on the appearance of the more mature cells of the stratum spinosum (squamatization). This pattern of inflammation causes the dermoepidermal interface to assume an angulated, zigzag contour (“sawtoothing”).
- Anucleate, necrotic basal cells are seen in the inflamed papillary dermis and are referred to as colloid bodies or Civatte bodies. Although these changes bear some similarities to those in erythema multiforme, lichen planus shows well-developed changes of chronicity, including epidermal hyperplasia, hypergranulosis, and hyperkeratosis.
Lichen planus is an uncommon disorder that usually presents in middle-aged adults.
- The cutaneous lesions are multiple and are usually symmetrically distributed, particularly on the extremities, and often occur about the wrists and elbows and on the glans penis.
- In approximately 70% of cases the oral mucosa is also involved, where the lesions manifest as white papules with a reticulate or netlike appearance.
- The cutaneous lesions of lichen planus usually resolve spontaneously within 1 to 2 years, but the oral lesions may persist and be of sufficient severity to cause trouble with food intake.
- There is no cure, but many different medications and procedures have been used in efforts to control the symptoms.