Lichen planus is a skin condition characterized by angular, purple bumps called papules that are inflammatory and pruritic (itchy). They may affect the skin, mucous membranes and nails. This noncontagious skin disease is usually mild and typically disappears without treatment in under a year, although severe cases may last much longer and may recur. Lichen planus usually affects adults between the ages of 30 and 60.

The cause of lichen planus is unknown, but it is thought to be an autoimmune disease, in which the body’s immune system attacks its own tissues. Some cases may be caused by exposure to certain chemicals (e.g., gold, iodides, antibiotics, diuretics).

Skin lesions characteristic of lichen planus may be very small or grouped together to form plaques. They are shiny, red or violet, flat-topped and covered in white spots or lines. They are usually itchy, may be scaly and their borders are distinct. They occur most often on the arms, legs, hands, feet, trunk and genitals. Mouth lesions are usually poorly defined gray-white or blue-white spots. When the nails are involved, they may be ridged, splitting, and/or thin. Hair or nail loss may also occur.

Lichen planus is typically diagnosed solely by the appearance of the lesions, although a skin biopsy from a lesion may be used to confirm the diagnosis. Treatment may not be needed. When given, treatment is generally focused on reducing symptoms (e.g., itching, inflammation) and speeding the healing time of the lesions. If the onset of lichen planus was linked to chemical exposure, it will typically clear up once this exposure has been discontinued. The most frequent treatments used are topical corticosteroids. Corticosteroids may also be injected directly into the lesions to ease itching. Severe cases may require systemic corticosteroid therapy, in either oral or injected forms.