|Classification and external resources|
Lichen planus affecting the shins.
Lichen planus is a chronic mucocutaneous disease that affects the skin, tongue, and oral mucosa. The disease presents itself in the form of papules,lesions, or rashes. Lichen planus does not involve lichens, the fungus/algae symbionts that often grow on tree trunks; the name refers to the dry and undulating, "lichen-like" appearance of affected skin. It is sometimes associated with oxidative stress, certain medications and diseases, however the underlying pathology is currently unknown.
Lichen planus may be divided into the following types:
- Morphology of lesion
- Site of involvement
- Special forms
Signs and symptoms
The typical rash of lichen planus is well-described by the "6 Ps": well-defined pruritic, planar, purple, polygonal papules and plaques. The commonly affected sites are near the wrist and the ankle. The rash tends to heal with prominent blue-black or brownish discoloration that persists for a long time. Besides the typical lesions, many morphological varieties of the rash may occur. The presence of cutaneous lesions is not constant and may wax and wane over time. Oral lesions tend to last far longer than cutaneous lichen planus lesions.
Oral lichen planus (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 reticular form is the easiest to diagnose. The bullas lesions must be differentiated from pemphigoid, chemical burns traumatic ulcers. When they break, they appear as ulcers and need to be differentiated from squamous cell carcinoma.
- The bullous form presents as fluid-filled vesicles which project from the surface.The atrophic and erosive forms must be differentiated from lichenoid drug reactions,SLE, pemphigoids and other immunobullous disease, candidiasis, erythema multiforme.
- The erosive forms (Atrophic LP & Ulcerative LP) present with erythematous (red) areas that are ulcerated and uncomfortable. The erosion of the thin epithelium may occur in multiple areas of the mouth (more prominent on the posterior buccal mucosa), 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, although this is controversial. The malignant transformation rate is thought to be less than 1%, however it has been reported to be as high as 5%. For any persistent oral lesion of erosive lichen planus that does not respond to topical corticosteroids, a biopsy is recommended to rule out precancerous (premalignant) change or malignant transformation.
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 with Civatte or colloid body formation. These result from degenerating epithelial cells.
- Infiltration of lymphocytic inflammatory cells into the subepithelial layer of connective tissue
- epithelial connective tissue interphase weakens resulting in formation of histological cleft known as Max. Joseph's space.
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.
Clinical experience suggests that Lichen planus of the skin alone is easier to treat as compared to one which is associated with oral and genital lesions.
Nail & hair loss is irreversible.
Lichen planus is not contagious and does not involve any known pathogen. Some lichen planus-type rashes (known as lichenoid reactions) occur as allergic reactions to medications for high blood pressure, heart disease and arthritis, in such cases termed drug-induced lichenoid reactions. These lichenoid reactions are referred to as lichenoid mucositis (of the mucosa) or dermatitis (of the skin). Lichen planus 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 skin (Lichenoid reaction of graft-versus-host disease). It has been suggested that true lichen planus may respond to stress, where lesions may present on the mucosa or skin during times of stress in those with the disease. Lichen planus affects women more than men (at a ratio of 3:2), and occurs most often in middle-aged adults. The involvement of the mucous membranes is seen frequently and usually is asymptomatic, but occasionally, LP can be complicated by extensive painful erosions. Lichen planus in children is rare.
Reactions to amalgam fillings may contribute to the oral lesions very similar to lichen planus, and a systematic review found that many of the lesions resolved after the fillings were replaced with another material.
Lichen planus can be part of Grinspan's syndrome.
Care of OLP is within the scope of oral medicine speciality. 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
- "lichen planus" at Dorland's Medical Dictionary
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- Penn State College of Medicine - Lichen Planus
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