Written by Dr. Pradeep

Lichen planus 

What is lichen planus?

Lichen planus (LP) is a chronic inflammatory condition affecting the skin and mucosal surfaces.

There are several clinical types

• Cutaneous lichen planus
• Mucosal lichen planus
• Lichen planopilaris
• Lichen planus of the nails
• Lichen planus pigmentosus
• Lichenoid drug eruption.

 Who gets lichen planus?

Lichen planus affects approximately 1% of the population worldwide, mostly affecting adults aged between 30 to 60 years. It has no strong racial predilection.

Approximately 10% of those affected have lichen planus of the nails while half of those affected have oral lichen planus, which is more common in women than in men.

What causes lichen planus?

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

• Genetic predisposition
• Physical and emotional stress
• Injury to the skin lichen planus often appears where the skin has been scratched or after surgery (koebnerisation)
• Localised skin disease such as herpes zoster
• Systemic viral infection, such as hepatitis C (which might modify self-antigens on the surface of basal keratinocytes)
• Contact allergy, such as to metal fillings in oral lichen planus (rare) and colour photographic developers
• Drugs; gold, quinine, quinidine, and others can cause a lichenoid rash.
  Lichenoid inflammation is also notable in graft-versus-host disease.

What are the clinical features of lichen planus?

• 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.
• Papules and polygonal plaques are shiny, flat-topped, and firm on palpation.
• The plaques are crossed by fine white lines called Wickham striae.
• Hypertrophic lichen planus can be a scaly and pruritic rash.
• Atrophic lichen planus is a rare annular variant with an atrophic centre.
• Annular lichen planus describes the development of violaceous plaques with central clearing often involving penis, scrotum, and intertriginous areas.
• Size ranges from pinpoint to larger than a centimetre.
• Distribution may be scattered, clustered, linear, annular, or actinic (sun-exposed sites such as face, neck, and backs of the hands).
• Location can be anywhere, but most often front of the wrists, lower back, and ankles.
• Colour depends on the patient’s skin type. New papules and plaques often have a purple or violet hue, except on palms and soles where they are yellowish-brown.
• Plaques resolve after some months to leave greyish-brown post-inflammatory macules that can take a year or longer to fade.

Oral lichen planus

The mouth is often the only affected area and 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:

• Painless white streaks in a lacy or fern-like pattern (Wickham striae)
• Painful and persistent erosions and ulcers (erosive LP)
• Diffuse redness and peeling of the gums (desquamative gingivitis)
• Localised inflammation of the gums adjacent to amalgam fillings.

Vulval lichen planus

Lichen planus may affect the labia majora, labia minora, and vaginal introitus. Presentation includes:

• Painless white streaks in a lacy or fern-like pattern
• Painful and persistent erosions and ulcers (erosive LP)
• Scarring, resulting in adhesions, resorption of labia minora and introital stenosis
• Painful desquamative vaginitis, preventing intercourse and causing a mucky vaginal discharge; the eroded vagina may bleed easily on contact
• Overlap with vulval lichen sclerosus that most commonly affects women over 50 years of age.

Penile lichen planus

• Classical papules in a ring around the glans.
• White streaks and erosive lichen planus may occur but are less common.

Other mucosal sites

Erosive lichen planus uncommonly affects the lacrimal glands, eyelids, external ear canal, oesophagus, larynx, bladder, and anus.

Lichen planopilaris

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 looking ‘like footprints in the snow’.

Nail lichen planus 

• Lichen planus affects one or more nails, sometimes without involving the skin.
• 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 rarely, completely disappear (anonychia).

Lichen planus pigmentosus

• Characterised by 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.
• Can be provoked by sun exposure, but it can also arise in sun-protected sites such as the armpits.
• Diffuse, reticulate, and diffuse patterns.
• Similar to erythema dyschromicum perstans and might be the same disease.
• Rarely affects the lips, resulting in a patchy dark pigmentation on upper and lower lips. 

Lichenoid drug eruption

• 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:Gold, Hydroxychloroquine

Quinine and thiazide diuretics cause a photosensitive lichenoid drug eruption.

Bullous lichen planus and lichen planus pemphigoides

Bullous lichen planus

• Produces blisters due to destruction of basal keratinocytes, and is rare.

Lichen planus pemphigoides

• Rare combination of lichen planus and bullous pemphigoid.
• Destruction of the basal keratinocytes exposes bullous pemphigoid antigen at the dermoepidermal junction (termed epitope spreading), followed by the development of circulating antibodies against BP antigen.
• Erythema and blisters develop both at the sites of and distant from lesions of lichen planus.

What is the treatment for lichen planus?

General measures

• Avoid soaps and shower gels that will exacerbate scaling.
• Use emollients regularly.
• Sedating antihistamines may help troublesome nocturnal itch.

Specific treatment

Treatment is not always necessary as cutaneous LP can be self-limiting and treatment goals are to manage pruritus. Local treatments for the symptomatic cutaneous or mucosal disease are:

• Potent topical corticosteroids
• Topical calcineurin inhibitors, tacrolimus ointment, and pimecrolimus cream
• Topical retinoids
• Intralesional steroid injections.

Systemic treatment for widespread lichen planus or severe local disease often includes a 1- to 3-month course of systemic steroids (eg, prednisone), while commencing another agent from the following list:

• Acitretin
• Hydroxychloroquine
• Methotrexate
• Azathioprine
• Mycophenolate mofetil
• Phototherapy. 

Anecdotal success is reported from long courses of antibiotics e.g. metronidazole, sulfasalazine, antifungals (such as griseofulvin), and JAK inhibitors. Lichen planopilaris is reported to improve with pioglitazone and tetracyclines. 

In oral lichen planus, limited evidence is found in using apremilast. Successful treatment of oral and cutaneous lichen planus with adalimumab has previously been reported. Tildrakizumab has been shown to demonstrate positive results in erosive oral lichen planus in an isolated case study.

In cases of oral lichen planus affecting the gums and buccal mucosa 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. 

For more information see, oral lichen planus and erosive lichen planus.

What is the outcome for lichen planus?

Lichen planus can have a chronic remitting and relapsing course. Cutaneous lichen planus tends to clear within a couple of years in most people, but post-inflammatory pigmentation may take years to subside.

Mucosal lichen planus is more likely to persist for a decade or longer. For lichen planopilaris, scarring is permanent, including scarring alopecia. Lichenoid drug eruption resolves slowly when the responsible medication is withdrawn.