* Oral lichen planus (OLP) affects about 50% of patients with skin lichen planus.
* May occur without skin lesions elsewhere.
* All areas inside the mouth can be affected, the commonest sites being the inner side of the cheeks (buccal mucosa), tongue, palate, gums and lips.
* There may be no symptoms but it can cause discomfort, severe pain and ulcers.
* Most cases are seen in middle-aged and much more common in women than in men (75% vs. 25%).
* Oral LP is stable but chronic, with less than 3% of patients having a spontaneous remission in an average 5-year follow-up.
* OLP has more prolonged course than the cutaneous form of the disease.

There are 3 clinical forms of OLP:
1. Reticular LP: symmetrical, asymptomatic, whitish papules in a lace-like pattern (network-like lesions). Occasionally, the papules coalesce forming large, irregular, whitish patches or plaques mimicking leukoplakia. It involves mainly the buccal mucosa (inner aspects of cheeks), and also the tongue or gums and may ulcerate. Plaque OLP is a form of reticular OLP and usually seen in smokers.
2. Erosive/ Ulcerative LP: a common variety usually presents as very painful red erosions often with a whitish border. It most often affects the gums and lips. SCC may complicate longstanding cases of this form of OLP.
3. Atrophic LP: is the rarest type presents as annular atrophic whitish patches.
* Many patients may have mixed types of OLP.
* LP may produce desquamative gingivitis which is particularly difficult to diagnose and often requires biopsy for both histology and DIF to confirm the diagnosis and exclude other autoimmune causes of desquamative gingivitis.
* Lichen planus may rarely (1%) lead to oral SCC which occurs only in patients with erosive/ ulcerative LP (doesn’t occur in the reticulate pattern). * Of the oral LP patients who develop oral SCC, about 45% have only one cancer. The majority develop multiple cancers, and close vigilance is recommended in these patients. So persistent oral ulcers should undergo biopsy.

Differential Diagnosis: The most important differentials are:
1. Oral Lichenoid Lesions (OLL) caused by medications (e.g. Gold), Dental Amulgum and Graft versus host disease.
2. Desquamative gingivitis caused by immunoblistering diseases.
3. Leukoplakia
4. SCC (Ulcerative LP)

Management of oral lichen planus: All available therapeutic modalities and options are unable to change the course of OLP. They may be useful in symptomatic relief or temporary clearance of the lesions.
I. Topical therapies:
(A) Topical numbing (LA) agents can be used to provide temporary relief for painful areas.

(B) Corticosteroids may reduce inflammation related to OLP. They may be given as a mouthwash, paste, ointment, gel or sprays applied directly to the mucous membrane (topical). Triamcinolone in an emollient dental paste or fluticasone nasal preparations are often prescribed. Intralesional triamcinolone injections may be used for focal unresponsive lesions.

(C) Retinoids: can be applied as a topical ointment, but they’re not commonly used to treat oral lichen planus. Topical treatment may irritate the mucous membranes of the mouth. Because topical retinoids also can cause birth defects, the drug shouldn’t be used by women who are pregnant or planning to become pregnant in the near future.

(D) Calcineurin Inhibitors: these can suppress or modify the immune response. They may be used as ointments, gels, or mouth rinse. Treatments that suppress immune system abnormalities may improve more severe lesions and lessen pain. Several reports have shown the effectiveness of topical calcineurin inhibitors in OLP. Examples of these topical medications include tacrolimus (Protopic) and pimecrolimus (Elidel). Topical tacrolimus 0.1% ointment has become standard treatment in erosive OLP. Burning may occur initially but can be reduced by concomitant use of topical steroids or initial use of a lower strength of tacrolimus ointment. Higher concentrations, up to 0.3%, also may be used. Most patients have a partial but significant response, with increased ability to eat with much less pain. Pimecrolimus can be used successfully in patients intolerant of topical tacrolimus. Sustained remissions are rare, and chronic use is usually required to maintain remission. Ciclosporine, another calcineurin inhibitor can be used as mouth rinse in OLP, however, it is ineffective.

II. Systemic therapies: are seldom used for OLP unless other parts of the body also are affected. However, when indicated (severe cases unresponsive to topical therapies or cases associated with involvement of other parts of the body), they may include:

(A) Systemic corticosteroids: 20-60 mg prednisone per day may control OLP but the main problem is the inevitable side effects.

(B) Systemic retinoids (acitretin or isotretinoin).

(C) Immunosupressives and Cytotoxics: Ciclosporine, Azathioprine, Cyclophsphamide, Mycophenolate mofetil and Methotrexate. All can induce remission in severe cases of cutaneous and oral LP.

(D) Heparin: Low-molecular-weight heparin (Enoxaparin), 3 mg injected subcutaneously once a week may result in remission of cutaneous and reticulate oral LP.

(E) Hydroxychloroquine in standard doses can be effective for cutaneous, oral, and genital LP.

(F) Thalidomide: 50–150 mg daily, can improve refractory oral and cutaneous LP.

(F) Others: Griseofulvin, Dapsone, Metronidazole.

(G) PUVA, photodynamic therapy, and 308-nm excimer laser have been effective in oral LP.