Lichen planus (LP) can occur on the skin alone; however, it is also seen inside the oral cavity, on the scalp, nails and the genital mucosa. Symptoms of lichen planus may wax and wane. They may increase during periods of trauma, or during stress and anxiety.

Cutaneous LP

Lichen planus is a papulosquamous skin disease which produces intense itching (pruritus). It consists of lesions which are characterized by six P’s:

• Pruritic
• Purplish
• Planar
• Polygonal
• Papules
• Plaques

The rash starts suddenly, and occurs on the inside of the wrists, the legs and the trunk. The lesions often show a lacy white network covering them, called Wickham’s striae. They may be shiny or be covered with scales.

Furthermore, the lesions often appear in lines, especially following lines of trauma such as a scratch or abrasion, which is called Koebner’s phenomenon. They may develop into vesicles or bullae in some cases, or become painful and ulcerated.

Forms of cutaneous LP

Cutaneous LP occurs in various forms, such as:

• Linear LP: these consist of close clusters of lesions following lines of trauma.
• Annular LP: seen in 10% of cases, this variant shows clusters of papules arranged in rings. The appearance may also be due to outward extension of the lesions while they clear towards the center. This type may affect the intertriginous areas, as well as the penis and the oral mucosa.
• Atrophic LP: this is rare, seen in the form of a few patches which show atrophy towards the surface.
• Hypertrophic LP: this form is mostly seen on the legs, including the ankles, shins and the interphalangeal joints. It is associated with the most intense itching. It also persists for a long time. When it clears, it leaves behind scarring and pigmentation of the affected area.
• Vesiculobullous LP: here the lesions are in the form of vesicles or larger bullae, which replace earlier papular lesions. They occur over the lower extremities, the back, the gluteal region or the buccal mucosa.
• Erosive LP: also known as ulcerative LP, these begin as painful ulcers within oral plaques. They are also seen on the soles as translucent lesions.

Oral LP

Oral LP typically consists of bluish-white papules, with the typical lacy white covering of Wickham’s striae, gradually enlarging. Although it is usually asymptomatic, the lesions may become ulcerated or spread, becoming very painful. The oral lesions typically affect the sides of the tongue, the buccal mucosa or the gingival mucosa.

In about a fourth of patients, the vulva or vagina is also involved. However, oral LP may also be accompanied by lesions in the scalp, the nails and the eyes. Pain, heat sensitivity, dryness of the mouth, a metallic taste and a burning sensation of the affected area may reduce the quality of life in ulcerative forms of oral LP.  

Forms of oral LP

Oral LP may take any of four forms:

• Erosive: this is the most painful type and consists of spreading erythematous lesions with irregular ulcers, often complicated by secondary fungal or bacterial infection.
• Reticular: this is the most common form. It consists of the appearance of Wickham’s striae on any part of the mucosa covering the inside of the mouth, the lips, palate, tongue or gums. It is usually bilateral and not associated with other symptoms.
• Papular: here the lesions are in the form of bluish-white or reddish spots
• Atrophic: here atrophic lesions showing gray or white Wickham’s striae occur against an erythematous oral mucosa.
• Bullous: this consists of large sacs filled with fluid, which break often to leave a painful erosion.

Genital LP

In men, it mostly affects the glans in an annular pattern. In women, linear white lines appear on the vulva or vagina. These may develop erosions, and be complicated by scarring of the vulval skin. This may cause urethral stenosis or vaginal narrowing.

The vulvovaginal lesions are usually pruritic, and may also be associated with burning or soreness. A yellowish or green vaginal discharge may also be seen. The presence of LP may cause severe discomfort during intercourse.

Lichen planopilaris and nail involvement

Lichen planopilaris is a form of the disease that occurs on the skin over the scalp and causes plugging of the hair follicles. It is responsible for hair loss.

If the nails are involved they shows irregular longitudinal grooves, but other nail abnormalities may also be seen such as:

• Nail detachment
• Atrophy of the nail plate
• Hypertrophy of the cuticle
• Subungual keratosis or hyperpigmentation