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Lichen planus (LP) is a non-infectious skin condition which causes itching and the appearance of papules and plaques over various parts of the body or the mucous membranes. It can be cutaneous or oral, and at some times it may be complicated by erosions.
Diagnosis of lichen planus is based on clinical grounds, namely, the appearance of the rash in the oral cavity or on the skin. Oral lichen planus lesions are often picked up first by dentists during routine dental check-ups.
The clinical presentation of lichen planus varies with the site and type of lesion.
The diagnosis of the lesions is by picking up the characteristic six P’s, namely:
Cutaneous lichen planus may occur in one of the following types:
In women, the vulva and vagina may show any of the following lesions:
Scalp and nail variants occur in only 10% of patients. In the scalp, it occurs as purplish lesions around a clump of hair follicles, with scaling and pruritus. It may result in scarring alopecia due to loss of hair follicles. Nail manifestations are diverse and range from:
Symptoms of oral lichen planus may vary. General symptoms include:
In some cases, patients with oral lichen planus present with cutaneous lesions, and the oral lesions are found only on examination. Genital lesions are present in up to 25% of women with oral lichen planus, but only up to 4% of men with similar location of lesions.
Oral lichen planus lesions may belong to one of the following six types:
In atypical cases of cutaneous lichen planus, the rash may be confused with other conditions, such as:
In some cases, oral lichen planus may be mistaken for:
In such cases, other investigations may be called for. The most common test is a 4-mm punch biopsy from an affected area, either on the skin or in the mouth. The most common pattern seen on microscopic examination of the biopsy is a “saw-tooth” pattern due to hyperplasia of the epidermis. There is a T-cell infiltrate at the dermo-epidermal junction, with vacuolar or liquefactive degeneration of the basal cells of the epidermis. The granular cell layer is thickened.
In many patients, the condition is associated with chronic hepatitis C. Thus testing for HCV is also performed in many patients, including HCV-RNA or HCV-specific CD4+ and CD8+ lymphocytes.
In vesiculobullous forms of lichen planus, the skin adjacent to the lesion may be taken for biopsy, as a direct immunofluorescence (IF) microscopy of the sample will differentiate other bullous lesions (such as pemphigus) from this condition. Direct IF shows the presence of autoantibodies bound to the skin cells.