The cause may be a reaction to certain drugs or infectious organisms.
Typical symptoms include an itchy rash made of red or purple bumps that form into scaly patches appearing on different parts of the body and sometimes in the mouth or on the genitals.
This disease can last for more than 1 year, and it can recur.
Drugs that may be causing lichen planus should be avoided.
Lichen planus usually resolves without treatment, but symptoms may be treated with corticosteroids, exposure to ultraviolet light, or lidocaine-containing mouthwashes.
The cause of lichen planus is not known, but it may be a reaction by the immune system to a variety of drugs (especially beta-blockers, nonsteroidal anti-inflammatory drugs [NSAIDs], angiotensin-converting enzyme [ACE] inhibitors, sulfonylureas, antimalarial drugs, penicillamine, and thiazides). The disorder itself is not infectious. Lichen planus of the mouth may occur in some people who have hepatitis C or, less commonly, possibly hepatitis B (see table The Hepatitis Viruses The Hepatitis Viruses 
).
Symptoms of Lichen Planus
The rash of lichen planus almost always itches, sometimes severely. The bumps are usually purple 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 (called hyperpigmentation).
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, and on the genital area. 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 is not common among children.
About half of people who get lichen planus also develop it in the mouth. Lichen planus in the mouth usually results in a lacy, bluish white patch that forms in lines and branches (called Wickham striae). 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.
Lichen planus affects the nails in up to 10% of cases. Some people may have only mild symptoms such as discoloration of the nail beds, thinning of the nails, and formation of nail ridges. Other people may completely lose their nails and have scarring from the cuticle at the base of the nail (the nail fold) to the skin under the nail (the nail bed).
Diagnosis of Lichen Planus
A doctor's evaluation
Skin biopsy
Doctors typically base the diagnosis of lichen planus on how the rash looks and where it appears on the body. However, because many other disorders can look like lichen planus (such as lupus erythematosus Systemic Lupus Erythematosus (SLE) Systemic lupus erythematosus is a chronic autoimmune inflammatory connective tissue disorder that can involve joints, kidneys, skin, mucous membranes, and blood vessel walls. Problems in the... read more 
on the body and candidiasis Symptoms 
or leukoplakia Precancerous changes in the mouth Growths can originate in any type of tissue in and around the mouth, including connective tissues, bone, muscle, and nerve. Growths most commonly form on the Lips Sides of the tongue Floor of... read more 
in the mouth), doctors typically do a biopsy (examination of tissue under a microscope).
Once diagnosed, doctors may do other liver tests Liver Blood Tests Liver tests are blood tests that represent a noninvasive way to screen for the presence of liver disease (for example, hepatitis in donated blood) and to measure the severity and progress of... read more and tests for hepatitis infections.
Prognosis for Lichen Planus
Lichen planus usually clears up by itself after 1 or 2 years, although it sometimes lasts longer, especially when the mouth is involved. Symptoms return 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. Mouth sores usually last for life.
Lichen planus in the vagina may be chronic and hard to treat, which decreases quality of life and may cause scarring.
Treatment of Lichen Planus
Measures to relieve itching
Corticosteroid injections, pills, or lotions
Phototherapy
Measures to relieve mouth pain
People who have no symptoms do not need treatment. Drugs that may be causing lichen planus should be avoided.
Lichen planus on the skin
Standard treatments can be used to relieve itching (see treatment of itching Treatment Itching can be very uncomfortable. It is one of the most common reasons people see doctors who specialize in skin disorders (dermatologists). Itching makes people want to scratch. Scratching... read more ).
Corticosteroids may be injected into the bumps, applied to the skin, or taken by mouth, sometimes with other drugs, such as acitretin, griseofulvin, or cyclosporine.
Phototherapy (exposure to ultraviolet light), sometimes combined with the use of psoralens (drugs that make the skin more sensitive to the effects of ultraviolet light) may also be helpful ( see Phototherapy: Using Ultraviolet Light to Treat Skin Disorders Phototherapy: Using Ultraviolet Light to Treat Skin Disorders ). Combining ultraviolet A light with psoralens is called PUVA (psoralen plus ultraviolet A). Use of a small band of ultraviolet B light is called narrowband ultraviolet light B (NBUVB).
Apremilast is a drug taken by mouth and is being studied as a treatment for women who have lichen planus in the vagina.
Lichen planus in the mouth
For painful mouth sores, a mouthwash containing lidocaine, an anesthetic, may be used before meals to form a pain-killing coating. Lidocaine mouthwashes should not be used more frequently than prescribed.
Tacrolimus ointment or corticosteroid mouthwashes, injections, or pills may also help mouth sores.
Dapsone taken by mouth or cyclosporine taken by mouth or as a mouth rinse may also help.
