Mucosal lichen planus
Mucosal lichen planus, or oral lichen planus (OLP), is lichen planus (an inflammatory auto-immune disease) that affects oral mucosa, with or without the involvement of the skin and other mucous membranes.
OLP affects women more than men (at a ratio of 3:2), and occurs most often in middle-aged adults. OLP in children is rare.
The cause of lichen planus is not known. It is not contagious and does not involve any known pathogen.
OLP has been reported as a complication of chronic hepatitis C virus infection and can be a sign of chronic graft-versus-host disease of the mucous membrane (and skin).
It has been suggested that OLP may respond to stress, where lesions may present on the mucosa (or skin) during times of stress in those with the disease.
Clinical presentation 
OLP may present in one of three forms.
- The reticular form is the most common presentation and manifests as white lacy streaks on the mucosa (known as Wickham's striae) or as smaller papules (small raised area). The lesions tend to be bilateral and are asymptomatic. The lacy streaks may also be seen on other parts of the mouth, including the gingiva (gums), the tongue, palate and lips.
- The bullous form presents as fluid-filled vesicles which project from the surface.
- The erosive form presents with erythematous (red) areas that are ulcerated and uncomfortable. The erosion of the thin epithelium may occur in multiple areas of the mouth, or in one area, such as the gums, where they resemble desquamative gingivitis. Wickham's striae may also be seen near these ulcerated areas. This form may undergo malignant transformation.
Rarely, lichen planus shows esophageal involvement, where it can present with erosive esophagitis and stricturing. It has also been hypothesized that it is a precursor to squamous cell carcinoma of the esophagus.
Histo-pathological appearance 
The microscopic appearance of lichen planus is pathognomonic for the condition
- Hyperparakeratosis with thickening of the granular cell layer
- Development of a "saw-tooth" appearance of the rete pegs
- Degeneration of the basal cell layer
- Infiltration of inflammatory cells into the subepithelial layer of connective tissue
- Max-joseph space is seen .
Differential Diagnosis 
The clinical presentation of OLP may also resemble other conditions, including:
- Lichenoid drug reaction. This entity is identical to OLP both clinically and histologically. However, lichenoid lesions may be single (in comparison to the usual bilateral appearance of OLP) with proximity to amalgam (metal alloys) dental restoration.
- Other oral vesiculo-ulcerative conditions such as Pemphigus vulgaris and Benign mucous membrane pemphigoid
- Discoid lupus erythematosus
- Chronic ulcerative stomatitis
- Frictional keratosis and Morsicatio buccarum (chronic cheek biting)
- Oral leukoplakia
- Chronic graft-versus-host-disease may manifest as lichenoid reaction. This type of lichenoid lesions have a higher risk of malignant transformation to oral squamous cell carcinoma in comparison to the classical oral lichen planus. Graft-versus-host-disease-associated oral cancer may have more aggressive behavior with poorer prognosis, when compared to oral cancer in non-hematopoietic stem cell transplantation patients.
A biopsy is useful in identifying histological features that help differentiate OLP from these conditions, except of the histologically identical lichenoid reaction lesion (including lichenoid reaction of graft-versus-host disease). Frictional keratosis and morsicatio buccarum can and should be diagnosed clinically without histo-pathlogical examination.
Care of OLP is within the scope of Oral medicine speciality. It is generally accepted that OLP (as well as other mucous membrane lichen planus, such as genital) is more difficult to manage than skin lichen planus.
Currently there is no cure for lichen planus but there are certain types of medicines used to reduce the effects of the inflammation. Lichen planus may go into a dormant state after treatment. There are also reports that lichen planus can flare up years after it is considered cured.
Medicines used to treat lichen planus include:
- Oral and topical steroids.
- Oral retinoids
- immunosuppressant medications
- Aloe vera
- Pusley Portulaca oleracea
- UVB NarrowBand Phototherapy
See also 
- Penn State College of Medicine - Lichen Planus
- Elad S, Zadik Y, Zeevi I, et al. (December 2010). "Oral cancer in patients after hematopoietic stem-cell transplantation: long-term follow-up suggests an increased risk for recurrence". Transplantation 90 (11): 1243–4. doi:10.1097/TP.0b013e3181f9caaa. PMID 21119507.
- Choonhakarn C, Busaracome P, Sripanidkulchai B, Sarakarn P (March 2008). "The efficacy of aloe vera gel in the treatment of oral lichen planus: a randomized controlled trial". Br. J. Dermatol. 158 (3): 573–7. doi:10.1111/j.1365-2133.2007.08370.x. PMID 18093246.
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