Table of Contents
Definition and Epidemiology of Lichen Planus
Lichen planus is an acquired, chronic, immune-mediated disease, manifesting as polygonal, purple, pruritic, planar papules or plaques on the skin and other lesions on the mucosal membranes, such as in the oral cavity.
Lichen planus is reported in less than 1% of the population. The incidence may increase in December and January. No significant geographical variation and no racial or sex predispositions have been observed. Children are rarely affected; most patients affected by lichen planus lie in the range of 30 – 60 years.
Etiology of Lichen Planus
- Genetics and familial.
- Chronic hepatitis C virus infection.
- Human herpesvirus type 7.
- Mercury (in dental amalgam, for oral lichen planus).
- Psychogenic factors, such as anxiety, depression, and stress.
Pathology and Pathophysiology of Lichen Planus
Lichen planus is thought to be an immunologically mediated disorder. It seems to be a CD8 cell-mediated response against antigens in the basal cell layer and the dermo-epidermal junction (mainly keratinocytes). The cause of this response is unknown, and exposure to certain viruses (e.g., hepatitis C and hepatitis B) or medications have been considered.
The immune-mediated damage to keratinocytes releases melanin into the dermis, leading to hyperpigmentation. The main pathology of the lesion is primarily found at the interface of the squamous epithelium and papillary dermis (interface dermatitis). At this junction, microscopically, a dense lymphocyte inﬁltration is seen.
The damaged basal keratinocytes often atrophy or become necrotic; they appear like the mature cells of the stratum spinosum (squamatization). This, in turn, causes saw toothing (angulated contour) of the interface. In the dermis, anucleate, necrotic basal cells (colloid or Civatte bodies) are seen. In addition to these changes, other features of lichen planus include epidermal hyperplasia, hypergranulosis, and hyperkeratosis.
Symptoms of Lichen Planus
The characteristic skin lesions of lichen planus are polygonal, purple, pruritic, planar papules, (remember four Ps) which may coalesce to form plaques. The lesions may be close together or widely separated from each other. They may have white dots or lines called Wickham striae; they may also be hyperpigmented.
The lesions are usually symmetrically distributed, often in extremities, particularly around the elbows and wrists. However, they may be found anywhere on the body, including on the glans penis and vulva. Usually, papules flatten in a few months and remain as areas of hyperpigmentation.
Mucous membrane (e.g., oral) lesions can be also found in patients with lichen planus; in 15% of cases, the involvement is predominant mucosal with minimal skin lesions.
In all, 50 – 70% of patients have oral lesions. These lesions can be whitish papules or plaques and/or white striae. They generally do not ulcerate, but this may occur due to epitheliomatous transformation. In women, sometimes, lichen planus manifests as desquamative inflammatory vaginitis.
Other variants of lichen planus include the following:
- Hypertrophic: Warty lesions, mainly on the lower limbs, which can persist for many years.
- Follicular (lichen planopilaris): Multiple, small, spiny lesions around hair follicles.
- Linear: Isolated linear lesions made up of papules close to each other.
- Actinic (lichen planus subtropical): Distinct discoid lesions with deeply hyperpigmented center surrounded by hypopigmented region; seen mainly in dark skin and young adults in tropical areas.
- Lichen planus pigmentosus: Diffuse or reticular macular hyperpigmentation.
- Annular: A few, large, discrete lesions, mainly on the penis and buccal mucosa.
- Atrophic: Few lesions, because of resolution or fading.
- Guttate: Wide scattered, small, discrete lesions.
Diagnosis of Lichen Planus
The diagnosis is usually established by clinical examination, although in doubtful or erosive cases, histopathology can help in differentiating from other similar diseases. In many cases, there may be comorbid conditions such as diabetes or oral candidiasis. These conditions should be checked for and treated accordingly. Wickham striae are usually seen in the oral lichen planus.
The differential diagnosis can be complicated if the lesions are atypical. The differential diagnosis will vary depending on the location of the lesion, and often the presence of lesions in other parts (skin or mucosa) can help rule out some other diseases. Some of the more common ones are listed below:
- Lichenoid drug eruptions
- Scratching-induced eczematous eruptions
- Lupus erythematosus
- Lichen sclerosis
- Secondary syphilis
- Erythema multiforme
- Leukoplakia, gingivitis, oral candidiasis, smoker’s patches (for oral lesions)
- Bullous diseases
Therapy of Lichen Planus
Most cases of lichen planus can be treated with topical class I and II corticosteroids (first-line treatment). Systemic corticosteroids are given when topical treatment fails or the disease is severe due to the involvement of the nails or scalp. However, systemic therapy is rarely needed due to the self-limiting nature of lichen planus.
For oral lesions, topical triamcinolone paste (0.1%) can be prescribed. Alternatively, 0.05% fluocinonide gel or ointment can also be applied bid or tid.
Oral prednisolone (0.5 mg to 1.0 mg/kg of body weight/day) or intramuscular triamcinolone (40-80 mg) for 4 to 6 weeks can be prescribed for severe mucosal lichen planus or nail lichen planus.
Oropharyngeal candidiasis and epidermal atrophy are common side effects of corticosteroids.
Retinoids are also prescribed for the treatment of oral lichen planus (OLP) with papular and plaque-like form. Retinoids may be prescribed alone or with the corticosteroids. Most commonly used retinoids are:
- Isotretinoin 0.1% gel
- Tretinoin 0.025%
- Oral acitretin, 30 mg/day for 8 weeks for cutaneous lichen planus (second-line treatment)
Tretinoin is effective only in OLP, but not effective in the cutaneous lesion.
Common adverse effects of retinoids are dyslipidemia, teratogenicity and liver enzyme elevations.
Body lesions in lichen planus can be treated with 0.05% of betamethasone dipropionate or diflorasone diacetate cream.
Several studies have recommended the usage of calcineurin inhibitors (tacrolimus or pimecrolimus) in steroid-unresponsive cases; however, they have the risk of causing lymphoma and skin cancers in adults and children.
For genital lesions, topical corticosteroids or calcineurin inhibitors are preferred.
Some other treatments have also been reported, but their efficacy is uncertain because of limited studies:
- Sulfasalazine, 2.5 g/day for 6 weeks
- Mycophenolate mofetil, 1–1.5 g, twice daily
- Apremilast (inhibitor of phosphodiesterase 4)
- Oral metronidazole (the mechanism is unknown)
However, relapses occur despite these effective treatments. For extensive, widespread disease, UV-B therapy or psoralen with UV-A (PUVA) therapy for 8 weeks can be given; however, PUVA therapy can be carcinogenic, as can be some medications.
Progression and Prognosis of Lichen Planus
The prognosis is good. Skin lesions usually resolve spontaneously within 1 year. The oral lesions may take longer to resolve. Recurrence/relapse is not uncommon. Ulcerative lesions on the oral mucosa can undergo malignant transformation (because of the high expression of cyclooxygenase-2), but the rate is very low (<2%).
Vulvar lichen planus can undergo transformation to or may be associated with squamous cell carcinoma. Very rarely, even skin lesions can give rise to squamous cell cancer. The following factors increase the risk of transformation of lichen planus lesions to squamous cell carcinoma: smoking, heavy alcohol consumption, erosive or atrophic lesions, erythroplakic lesions, and mucosal involvement.