Lichen planus is an immune-mediated disease resulting in an itchy skin rash which sometimes affects the inside of the mouth. It can also affect several other body parts, including the nails, scalp (lichen planopilaris), genitals, eyes, throat, and digestive tract. This disease is not contagious. It often resolves itself and heals within one year in the skin, but can be chronic in the skin and in other areas. It affects 0.1-4% of the population; patients are usually 30-60 years old, and women are more likely to get the disease than men.

Lichen Planus of the Skin

Lichen planus affects the skin, presenting as a rash of flat-topped purple itchy areas. This rash may also vary in appearance according to the following patterns:

Linear lichen planus: Lines that are close together

Annular lichen planus: Groups of lesions that become rings

Atrophic lichen planus: A few well-defined lesions with thinning of the skin. Not common.

Hypertrophic lichen planus: Scarring, often chronic, darkens the skin and occurs on the limbs

Vesiculobullous lichen planus: Fluid-filled blisters. Not common.

Erosive/ulcerative lichen planus: Painful blisters and sores on the feet. Not common.

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Severe itching is a major complaint from patients with lichen planus of the skin. After the rash heals, the affected skin is often darker than normal (post-inflammatory hyperpigmentation), especially in dark-skinned patients.

Oral Lichen Planus

Lichen planus may occur on the insides of the cheek, sides of the tongue, and gums and often occurs with other types of lichen planus. It is usually not painful but can be when it occurs with erosive/ulcerative lichen planus.

Causes

The cause of lichen planus is not fully understood, but it is thought to be an autoimmune disease that involves T cells. Many T cells can be seen around areas of the skin that are affected by lichen planus. These T cells destroy the surrounding tissue, which results in the lesions that we see in lichen planus. However, it is unknown what triggers the T cells to enter these sites and attack these tissues. There are thought to be certain genetic factors that can make someone more likely to have lichen planus.

Associated Diseases

Many autoimmune disorders are associated with lichen planus, especially related to hair loss and digestive tract disorders. Patients with lichen planus are also five times more likely to have hepatitis C infection, although the relationship between these two diseases is not understood. Some types of medications, and dental procedures, such as the removal or placement of a filling, are also associated with lichen planus.

Treatment

Lichen planus is most commonly treated with topical corticosteroids to dampen the immune response. For lichen planus, corticosteroids and some other agents which block the immune system may be used to prevent T cells from attacking the affected areas and causing lesions.

Other treatments less commonly used are topical retinoids, oral retinoids, and phototherapy. Topical retinoids can cause dryness, redness, and sun sensitivity and all retinoids can be harmful to the fetus in pregnant women. Side effects of prolonged use of phototherapy are an increased risk of hyperpigmentation, especially in dark-skinned patients, and skin cancer. Oral antihistamines can also be given to reduce itching. Reticular oral lichen planus usually does not require treatment because it is painless.

Outcomes

Skin disease spontaneously heals after about one year and more quickly with treatment, but the affected area usually remains darker than normal. Treatment of erosive and ulcerative oral disease can reduce pain and heal sores, but the condition can be chronic in some patients. Other forms of lichen planus are chronic, so the treatment goal is to reduce pain and prevent or limit scarring. Treatment may significantly improve disease of the scalp and nails, but these forms of the disease often recur. Complete resolution of genital disease is uncommon.