Lichen planus is an autoimmune inflammatory disorder than can affect both the skin and mucosal surfaces. It is named for its resemblance to Lichen, an organism composed of fungus and algae.
Lichen planus mainly affects middle- aged adults between 30 and 60 years old. Childhood cutaneous lichen planus is uncommon.
The classic presentation of cutaneous lichen planus is described by the four “P’s”: pruritic, purple, polygonal, and papules or plaques. The lesions seen in lichen planus are often extremely pruritic, or itchy.
This rash can present as plaques, which are solid, raised, flat topped lesions that are larger than 1 cm in area. Plaques often form after the formation of papules the same as plaques except less than 1 cm in diameter.
The lesions are often referred to as purple-colored “violaceous” lesions with a polygonal shape.
Lichen planus can present with mucosal and genital involvement. Genital lichen planus usually presents as violaceous papules on the glans penis or the vulva.
Fine white lines, also known as Wickham’s striae may be visible on the surfaces of the papules or plaques seen in lichen planus.
Many cases of lichen planus can be diagnosed clinically. If the diagnosis is uncertain, a skin biopsy can provide a definitive diagnosis.
On biopsy there is a “sawtooth” infiltrate of lymphocytes at the dermal- epidermal junction.
Lichen planus is usually self limited and topical corticosteroids are commonly used as first line treatment. Cutaneous lichen planus often spontaneously resolves after a few years, but lichen planus affecting the oral mucosa, genital mucosa, scalp and nails tends to be more chronic.
The association between hepatitis C virus (HCV) and lichen planus is controversial. Therefore, it has not been established if those with lichen planus need routine screening for HCV infection.
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