Lichen planus is an itchy eruption characterized by papular, purple (violaceous color), polygonal lesions which are located on distal extremities but may also affect genitalia or mucous membranes. It has a predilection for the flexor aspects of the forearms and dorsum of the hands.
It can occur at any age but is most common in the age group of 30-60 years. There is no gender predilection.
Pathophysiology of Lichen Planus
The exact cause of lichen planus is not known, although it is immunologically mediated. The initiating antigen is unclear.
Langerhans cells are known to process the antigen to T lymphocytes, resulting in an epidermotropic infiltrate.
Following associations have been noted
- Positive family history – These families are found to have increased frequency of human leukocyte antigen B7, HLA-DR1, and DR10
- Found with other immune-related diseases like ulcerative colitis, alopecia areata, vitiligo, dermatomyositis, lichen sclerosis, and myasthenia gravis
- Also found in hepatitis C virus infection, chronic active hepatitis, and primary biliary cirrhosis
- Precipitated by certain drugs- called lichenoid drug eruptions [These do not involve the oral mucosa]
- Delayed type of graft-versus-host reaction which may occur after marrow transplantation may also manifest as lichen planus.
Presentation of Lichen Planus – Symptoms and Signs
Most cases are of insidious onset. Lesions usually develop on flexural surfaces of the limbs, such as the wrists. After a week or more, a generalized eruption develops with maximal spreading within 2-16 weeks.
The face is generally not involved. The itching, when occurs is usually severe.
In some patients, the lesions are very dark while in others these may be light pink. The surface of the lesions, however, is almost always smooth and shiny.
The morphology of the lesion may vary with the type of lichen planus. [See types of Lichen Planus below]
In addition to the skin, lichen planus can involve the mucous membranes, the genitalia, the nails, and the scalp.
The lesions are usually 3-5 mm in diameter and the larger lesions may have whitish criss-cross streaks on their surface (Wickham’s striae).
Some lesions may be situated along a scratch mark representing Koebner phenomenon.
Pruritus or itching is common in lichen planus but varies in severity with the type of lesion and the extent of involvement. Hypertrophic lesions are extremely itchy.
Mucous membrane involvement is common and may be present without the skin lesions.
Nearly 60 percent of the cases have associated mucosal lesions which are whitish papules, whitish streaks criss-crossing to form a lacy pattern or superficial ulcerations. Such lesions may be located on the lips, tongue, buccal mucosa, gingival mucosa, conjunctivae, the larynx, the esophagus, the tonsils, the tympanic membrane, gastrointestinal tract, around the anus, glans penis and rarely vaginal and/or rectal mucosa.
In some cases, lichen planus may occur only on the mucous membranes without skin lesions.
The lacy pattern of the mucosal lesions is quite characteristic of lichen planus and helps to make the diagnosis.
Oral lesions are classified as
Genital involvement is common.
Men develop annular lesions on the glans. Wickham striae may also be observed.
Vulvar involvement can range from reticulate papules to severe erosions.
Dyspareunia [pain during intercourse], a burning sensation, and pruritus are common in women.
50% of women with oral lichen planus are found to have undiagnosed vulvar lichen planus also.
Approximately 10% of the cases have involvement of the nails which in the mildest form may show slight roughness of the nail plate with longitudinal ridging and brittleness of the nail plate with flaking (onychorrhexis).
In severer forms of involvement, the nail plate may become thin and small, it may be reduced to a few longitudinal strands of the nail plate or there may even be complete disappearance of the nail plate (anychia).
As the nail plate becomes smaller and smaller, a fold of skin from the posterior nail fold starts over-growing the nail plate to form a pterygium of the nail.
Anychia and pterygium are quite characteristic findings of lichen planus and sometimes these may be the only manifestations of lichen planus.
The changes may start in one or more nails but usually, the other nails are also involved in due course.
Follicular and perifollicular lesions on the scalp, which may be violaceous, scaly, and pruritic papules are found.
These can lead to atrophic cicatricial alopecia [loss of hair], known as lichen planopilaris. Alopecia can appear even many weeks after the skin lesions have disappeared.
Alopecia could be permanent.
In some patients, the disease progresses slowly and there are only a few lesions, while in others, the disease may spread quickly with the appearance of hundreds of lesions on the trunk and extremities. Rarely, lichen planus may change to exfoliative dermatitis.
Types of Lichen Planus
Hypertrophic lichen planus
These are most often found on the extensor surfaces of the lower extremities, especially around the ankles. Hypertrophic lesions are extremely itchy and can leave residual pigmentation and scarring when the lesions eventually clear.
Atrophic lichen planus
There are few lesions. This type is often noticed in case of resolution of annular or hypertrophic lesions.
Erosive/ulcerative lichen planus
These lesions are found on the mucosal surfaces.
Follicular lichen planus
It is also called lichen planopilaris and is characterized by keratotic papules that may coalesce into plaques.
This condition is more common in women. Nail and mucosal involvement are more likely to be present.
It may result in scarring alopecia.
Annular lichen planus
It is a rare variety. Annular lesions with an atrophic center can be found on the buccal mucosa and the male genitalia.
Linear lichen planus
Isolated linear lesions may develop as a Köebner effect.
Vesicular and bullous lichen planus
These lesions develop on the lower limbs or in the mouth from preexisting lichen planus lesions. Lichen planus pemphigoides is a combination of both lichen planus and bullous pemphigoid.
Actinic lichen planus
Lesions are characterized by discoid patches with a hypopigmented zone surrounding a hyperpigmented center This is also called subtropic lichen planus and occurs in regions like Africa, the Middle East, and India. They are mildly itchy. Usually spares the nails, the scalp, the mucous membranes, and covered areas.
Lichen planus pigmentosus
This is a rare variant that appears on face and neck. Found more in dark-skinned persons.
Lichen planus pemphigoides
This is also a rare variant where blisters subsequently develop on lichen planus lesions. It resembles bullous pemphigoid, but carries a better prognosis.
Differential Diagnoses of Lichen Planus
- Skin manifestations of Graft Versus Host Disease
- Guttate Psoriasis
- Lichen Nitidus
- Lichen Simplex Chronicus
- Pediatric Syphilis
- Pityriasis Rosea
- Plaque Psoriasis
- Tinea Corporis
Direct immunofluorescence in lichen planus reveals globular deposits of immunoglobulin M and complement mixed with apoptotic keratinocytes.
No imaging studies are necessary for lichen planus.
- Irregular acanthosis and colloid bodies in the epidermis with destruction of the basal layer.
- Bandlike infiltrate of lymphocytes and histiocytes in upper dermis, often disrupting the dermal-epidermal junction
- Degenerative keratinocytes, known as colloid or Civatte bodies, are found in the lower epidermis.
Treatment of Lichen Planus
Lichen planus is a self-limited disease that usually resolves within 8-12 months. Mild cases can be treated with fluorinated topical steroids but severe cases need more intensive treatment.
- Topical steroids are the first-line treatment of cutaneous lichen planus.
Systemic steroids provide better symptom control and more rapid resolution. Intramuscular steroids like triamcinolone 40-80 mg every 6-8 weeks can also be given.
- Oral metronidazole has been shown to be effective in some patients. Its mechanism of action is not known.
- Oral acitretin [retinoid agent] has been shown to be effective. Close monitoring of lipid levels is suggested with oral retinoid use.
- Other drugs under study are mycophenolate mofetil and sulfasalazine, apremilast.
- Patients with widespread lichen planus may be considered for UV-B therapy or Psoralen with UV-A therapy.
Complications of Lichen Planus
- Oral ulcerations associated with lichen planus have the potential to become malignant.
- Infection, osteoporosis, adrenal insufficiency, bone marrow suppression, renal damage, hyperlipidemia, and growth retardation in children may occur due to medication.
- Alopecia is often permanent.
- Hypertrophic lesions may leave residual hyperpigmentation.
- Vulvar and urethral stenosis may be a complication.
Prognosis of Lichen Planus
The prognosis for lichen planus is good, as most cases regress within 18 months. Some cases recur.
In about 50% of patients with skin disease, the lesions resolve within 6 months. Within 18 months 85% of the cases subside.
Large, annular, hypertrophic lesions and mucous membrane involvement are more likely to become chronic.
Some cases may persist for even 10 to 20 years.