Lichen planus, a recurring itchy disease, starts as a rash of small, discrete red or purple bumps that then combine and become rough, scaly patches.
The cause of lichen planus is not known, but it may be a reaction by the immune system to a variety of drugs (especially gold, bismuth, arsenic, quinine, quinidine, and quinacrine), chemicals (especially certain chemicals used to develop color photographs), and infectious organisms. The disorder itself is not infectious.
The rash of lichen planus almost always itches, sometimes severely. The bumps are usually violet and have angular borders. When light is directed at the bumps from the side, the bumps display a distinctive sheen. New bumps may form wherever scratching or a mild skin injury occurs. Sometimes a dark discoloration remains after the rash heals.
Usually, the rash is evenly distributed on both sides of the body—most commonly on the torso, on the inner surfaces of the wrists, on the legs, on the head of the penis, and in the vagina. About half of those who get lichen planus also develop mouth sores. The face is less often affected. On the legs, the rash may become especially large, thick, and scaly. The rash sometimes results in patchy baldness on the scalp.
Lichen planus in the mouth usually results in a bluish white patch that forms in lines. This type of mouth patch often does not hurt, and the person may not know it is there. Sometimes painful sores form in the mouth, which often interfere with eating and drinking.
Prognosis and Treatment
Lichen planus usually clears up by itself after 1 or 2 years, although it sometimes lasts longer, especially when the mouth is involved. Symptoms recur in about 20% of people. Prolonged treatment may be needed during outbreaks of the rash. However, between outbreaks, no treatment is needed. People with mouth sores have a slightly increased risk of oral cancer, but the rash on the skin does not turn cancerous.
Drugs or chemicals that may be causing lichen planus should be avoided, and standard treatments can be used to relieve itching (see Itching and Noninfectious Rashes: Treatment). Corticosteroids may be injected into the bumps, applied to the skin, or taken by mouth, sometimes with other drugs, such as acitretin or cyclosporine. Phototherapy (exposure to ultraviolet light) combined with the use of psoralens (drugs that make the skin more sensitive to the effects of ultraviolet light) may also be helpful. This treatment is called PUVA (psoralens plus ultraviolet A). For painful mouth sores, a mouthwash containing lidocaine, an anesthetic, may be used before meals to form a pain-killing coating.
Last full review/revision December 2006 by Peter C. Schalock, MD