Lichen planus is an inflammatory condition of the skin and mucous membranes. It mostly occurs when the immune system mistakenly attacks the cells of the skin or mucous membranes. Lichen planus usually heals on its own and is not as dangerous as leukoplakia.
Lichen planus can be defined as 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 the following causes mentioned below
- Genetic predisposition can be seen.
- Physical and emotional stress may add to the cause.
- Injury to the skin due to any reason, lichen planus often appears where the skin has been scratched or after surgery, etc.
- Can occur due to localised skin disease such as herpes zoster.
- Systemic viral infection, such as hepatitis C can also contribute to the cause
- Contact allergies due to metal fillings in oral lichen planus.
- Use of drugs, quinine, quinidine, and others can cause a lichenoid rash which can be a cause.
- Lichenoid inflammation can also be noticed in graft-versus-host disease.
Lichen planus has several forms, those are mentioned below
- Actinic (in sun-exposed areas)
- Hypertrophic lichen planus may resemble squamous cell carcinoma which is a skin disease. However, rarely, longstanding erosive lichen planus can result in a cancerous condition called squamous cell carcinoma, most often in the mouth, vulva, or penis. This should be suspected with the symptoms like if there is an enlarging nodule or an ulcer with thickened edges.
- Cancer is very common in smokers, those with a history of cancer in mucosal sites.
- Oesophageal lichen planus can also cause dysphagia, strictures, and possibly squamous cell carcinoma.
- Cancer from other forms of lichen planus is rare other than the above-mentioned types.
In most of the cases lichen planus is diagnosed clinically. A skin biopsy is often recommended to confirm the diagnosis and to look for cancer.
Typical features include the following
- Irregularly thickened epidermis is observed
- Wedge-shaped hypergranulosis, saw-tooth shaped rete ridges can be seen
- Civatte bodies are present in the lower epidermis and upper dermis
- Liquefaction degeneration of the basal layer of the epidermis is seen
- Band-like lymphocytic infiltrate at the dermo-epidermal junction can be observed.
Direct immunofluorescence studies are not needed often as these results may reveal colloid bodies in the papillary dermis with irregular deposits.
Patch testing may be recommended for patients with oral lichen planus affecting the gingiva and who have amalgam fillings in the oral cavity, to assess for contact allergy to other metals.
- Avoiding soaps and shower gels that exacerbate scaling is useful.
- Use of emollients regularly can help.
- Sedating antihistamines may help discomfort from nocturnal itching.
Treatment is not always necessary as cutaneous Lichen planus can be self-limiting and treatment goals are mostly to manage pruritus.
Local treatments for the symptomatic cutaneous or mucosal disease are mentioned below
- Potent topical corticosteroids
- Topical calcineurin inhibitors
- Tacrolimus ointment
- Pimecrolimus cream
- Topical retinoids
- Intralesional steroid injections.
Systemic treatment for lichen planus mostly includes a 1- to 3 months course of systemic steroids (eg prednisone), while commencing another agent from the following list
- Mycophenolate mofetil
Lichen planopilaris is reported to improve with pioglitazone and tetracyclines.
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.