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Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 1997. Updated, October 2015.
Lichen planus is a chronic inflammatory skin condition affecting the skin and mucosal surfaces. There are several clinical types of lichen planus that share similar features on histopathology.
Lichen planus affects about one in one hundred people worldwide, mostly affecting adults over the age of 40 years. About half those affected have oral lichen planus, which is more common in women than in men. About 10% have lichen planus of the nails.
Lichen planus is a T cell-mediated autoimmune disorder, in which inflammatory cells attack an unknown protein within the skin and mucosal keratinocytes.
Contributing factors to lichen planus may include:
A lichenoid inflammation is also notable in graft-versus-host disease, a complication of a bone marrow transplant.
Lichen planus may cause a small number or many lesions on the skin and mucosal surfaces.
The usual presentation of the disease is classical lichen planus. Symptoms can range from none (uncommon) to intense itch.
Cutaneous lichen planus
The mouth is often the only affected area. Oral lichen planus often involves the inside of the cheeks and the sides of the tongue, but the gums and lips may also be involved. The most common patterns are:
Oral lichen planus
Lichen planus may affect labia majora, labia minora and vaginal introitus. Presentation includes:
Penile lichen planus usually presents with classical papules in a ring around the glans. White streaks and erosive lichen planus may occur but are less common.
Erosive lichen planus uncommonly affects the lacrimal glands, eyelids, external ear canal, oesophagus, larynx, bladder and anus.
Lichen planopilaris presents as tiny red spiny follicular papules and extending smooth areas on the scalp or less often, elsewhere on the body. Rarely, blistering occurs in the lesions. Destruction of the hair follicles leads to permanently bald patches characterised by sparse 'lonely hairs'.
Frontal fibrosing alopecia is a form of lichen planopilaris that affects the anterior scalp, forehead and eyebrows.
Pseudopelade of Brocq may be a variant of lichen planus without inflammation or scaling. Areas of scarring without hair slowly appear, described as 'like footprints in the snow'.
Lichen planus affecting the scalp
Lichen planus affects one or more nails, sometimes without involving the skin surface. It is called twenty-nail dystrophy if all nails are abnormal and nowhere else is affected. Lichen planus thins the nail plate, which may become grooved and ridged. The nail may darken, thicken or lift off the nail bed (onycholysis). Sometimes the cuticle is destroyed and forms a scar (pterygium). The nails may shed or stop growing altogether, and they may rarely, completely disappear (anonychia).
Lichen planus of nails
Lichen planus pigmentosus describes ill-defined oval, greyish brown marks on the face and neck or trunk and limbs without an inflammatory phase. It is a form of acquired dermal macular hyperpigmentation. It can be provoked by sun exposure, but it can also arise in sun-protected sites such as the armpits. It has diffuse, reticulate and diffuse patterns. Lichen planus pigmentosus is similar to erythema dyschromicum perstans and might be the same disease.
Lichen planus pigmentosus may rarely affect the lips, resulting in a patchy dark pigmentation on upper and lower lips.
Lichen planus pigmentosus
Lichenoid drug eruption refers to a lichen planus-like rash caused by medications. Asymptomatic or itchy; pink, brown or purple; flat, slightly scaly patches most often arise on the trunk. The oral mucosa (oral lichenoid reaction) and other sites are also sometimes affected. Many drugs can rarely cause lichenoid eruptions. The most common are:
Quinine and thiazide diuretics cause a photosensitive lichenoid drug eruption.
Hypertrophic lichen planus may resemble squamous cell carcinoma. However, rarely, longstanding erosive lichen planus can result in true squamous cell carcinoma, most often in the mouth (oral cancer) or on the vulva (vulval cancer) or penis (penile cancer). This should be suspected if there is an enlarging nodule or an ulcer with thickened edges in these sites. Cancer is more common in smokers, those with a history of cancer in mucosal sites, and in those who carry sexually acquired and oncogenic human papillomavirus.
Cancer from other forms of lichen planus is rare.
In most cases, lichen planus is diagnosed by observing its clinical features. A biopsy is often recommended to confirm or make the diagnosis and to look for cancer. The histopathological signs are of a lichenoid tissue reaction affecting the epidermis.
Typical features include:
Direct immunofluorescent staining may reveal deposits of immunoglobulins at the base of the epidermis.
Treatment is not always necessary. Local treatments for the symptomatic cutaneous or mucosal disease are:
Systemic treatment for widespread lichen planus or severe local disease often includes a 1 to 3-month course of oral prednisone, while commencing another agent from the following list:
In cases of oral lichen planus affecting the gums with contact allergy to mercury, the lichen planus may resolve on replacing the fillings with composite material. If the lichen planus is not due to mercury allergy, removing amalgam fillings is very unlikely to result in a cure.
Cutaneous lichen planus tends to clear within a couple of years in most people, but mucosal lichen planus is more likely to persist for a decade or longer. Spontaneous recovery is unpredictable, and lichen planus may recur at a later date. Scarring is permanent, including balding of the scalp.
Lichenoid drug eruptions clear up slowly when the responsible medication is withdrawn.
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