Lichen planus is a disorder of the skin and mucous membranes resulting in inflammation, itching, and distinctive skin lesions.

Lichen planus is an uncommon disorder involving a recurrent, itchy, inflammatory rash or lesion on the skin or in the mouth. The exact cause is unknown, but the disorder is likely to be related to an allergic or immune reaction.

The disorder has been known to develop after exposure to potential allergens such as medications, dyes, and other chemical substances. Symptoms are increased with emotional stress, possibly because of changes in immune system during stress.

Lichen planus generally affects middle age adults. It is less common in children. The initial attack may last for weeks to months, and come and go for years.

Lichen planus may be associated with several other disorders, most notably hepatitis C.

Chemicals or medications associated with development of lichen planus include gold (used to treat rheumatoid arthritis), antibiotics, arsenic, iodides, chloroquine, quinacrine, quinidine, antimony, phenothiazines, diuretics such as chlorothiazide, and many others.

• Itching in the location of a lesion, mild to severe
• Skin lesion:
  • Usually located on the inner areas of the wrist, legs, torso, or genitals
  • Generalized, with symmetric appearance
  • Single lesion or clusters of lesions, often at sites of skin trauma
  • Papule of 2 - 4 cm size
  • Papules clustered into a plaque or large, flat-topped lesion
  • Distinct, sharp borders to lesions
  • Possibly covered with fine white streaks or linear scratch marks called Wickham's striae
  • Shiny or scaly appearance
  • Color dark -- reddish-purple (skin) or gray-white (mouth)
  • Possibility of developing blisters or ulcers
• Ridges in the nails (nail abnormalities)
• Dry mouth
• Metallic taste in the mouth
• Mouth lesions
  • Tender or painful (mild cases may have no discomfort)
  • Located on the sides of the tongue or the inside of the cheek
  • Occasionally located on the gums
  • Poorly defined area of blue-white spots or "pimples"
  • Linear lesions forming a lacy-appearing network of lesions
  • Gradual increase in size of affected area
  • Lesions occasionally erode to form painful ulcers
• Hair loss

A preliminary diagnosis may be made on the way your skin or mouth lesions look. A skin lesion biopsy or biopsy of a mouth lesion can confirm the diagnosis. Additional blood tests may be done to rule out hepatitis.