The cause of lichen planus is not known, however there are cases of lichen planus-type rashes (known as lichenoid reactions) occurring as allergic reactions to medications for high blood pressure, heart disease and arthritis. These lichenoid reactions are referred to as lichenoid mucositis (of the mucosa) or dermatitis (of the skin). Lichen planus has been reported as a complication of chronic hepatitis C virus infection. It has been suggested that true lichen planus may respond to stress, where lesions may present on the mucosa or skin during times of stress in those with the disease. Lichen planus affects women more than men 3:2, and occurs most often in middle-aged adults. Lichen planus in children is rare.

Clinical features

The typical rash of lichen planus takes the form of well-defined, purplish, polygonal, extremely itchy bumps on the skin. The commonly affected sites are near the wrist and the ankle. The rash tends to heal with prominent blue-black or brownish discoloration that persists for a long time. Besides the typical lesions, many morphological varieties of the rash may occur.

The presence of lesions is not constant and may wax and wane over time.

Inside the mouth, the disease may present in the (1) reticular form or in the (2) erosive form. (1) The reticular form is the more common presentation and manifests as white lacy streaks on the mucosa (known as Wickham's striae) or as smaller papules (small raised area). The lesions tend to be bilateral and are asymptomatic. The lacy streaks may also be seen on other parts of the mouth, including the gingiva (gums), the tongue, palate and lips. (2) The erosive form presents with erythematous (red) areas that are ulcerated and uncomfortable. The erosion of the thin covering of cells (the epithelium) may occur in multiple areas of the mouth, or in one area, such as the gums. Wickham's striae may also be seen near these ulcerated areas.

Lichen planus may also affect the genital mucosa. It can resemble other skin conditions such as atopic dermatitis and psoriasis.

Differential Diagnosis

The clinical presentation of lichen planus may also resemble other conditions, including:

Lichenoid drug reaction
Lupus Erythematosus
Chronic Ulcerative Stomatitis
Pemphigus Vulgaris
Benign Mucous Membrane Pemphigoid

A biopsy is useful in identifying histological features that help differentiate lichen planus from these conditions.

Cure

Currently there is no cure for lichen planus but there are certain types of medicines used to reduce the effects of the inflammation. Lichen planus may go into a dormant state after treatment. There are also reports that lichen planus can flare up years after it is considered cured.

Definition

Lichen planus is a skin condition of unknown origin that produces small, shiny, flat-topped, itchy pink or purple raised spots on the wrists, forearms or lower legs, especially in middle-aged patients.

Description

Lichen planus affects between 1-2% of the population, most of whom are middle-aged women. The condition is less common in the very young and the very old. The lesions are found on the skin, genitals, and in the mouth. Most cases resolve spontaneously within two years. Lichen planus is found throughout the world and is equally distributed among races.

Causes & symptoms

No one knows what causes lichen planus, although some experts suspect that it is an abnormal immune reaction following a viral infection, probably aggravated by stress. The condition is similar to symptoms caused by exposure to arsenic, bismuth, gold, or developers used in color photography. Occasionally, lichen planus in the mouth appears to be an allergic reaction to medications, filling material, dental hygiene products, chewing gum or candy.

Symptoms can appear suddenly, or they may gradually develop, usually on the arms or legs. The lesions on the skin may be preceded by a dryness and metallic taste or burning in the mouth.

Once the lesions appear, they change over time into flat, glistening, purple lesions marked with white lines or spots. Mild to severe itching is common. White, lacy lesions are usually painless, but eroded lesions often burn and can be painful. As the lesions clear up, they usually leave a brown discoloration behind, especially in dark skinned people.

Lichen planus in the mouth occurs in six different forms with a variety of symptoms, appearing as lacy-white streaks, white plaques, or eroded ulcers. Often the gums are affected, so that the surface of the gum peels off, leaving the gums red and raw.

Diagnosis

A doctor can probably diagnose the condition simply from looking at the characteristic lesions, but a skin biopsy may be needed to confirm the diagnosis.

Treatment

Treatment is aimed at easing symptoms. Itching can be treated with steroid creams and oral antihistamines. Severe lesions can be treated with corticosteroids by mouth, or combinations of photochemotherapy (PUVA) and griseofulvin.

Patients with lesions in the mouth may find that regular professional cleaning of the teeth and conscientious dental care improve the condition. Using milder toothpastes instead of tartar control products also seems to lessen the number of ulcers and makes them less sensitive.

Prognosis

While lichen planus can be annoying, it is usually fairly benign and clears up on its own. It may take months to reach its peak, but it usually clears up within 18 months.

Key Terms

PUVA: A type of phototherapy that combines the oral or topical photosensitizing chemical psoralen, plus long-wave ultraviolet light-A (UVA).

Gale Encyclopedia of Medicine. Gale Research, 1999.

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