Lichen planus is a chronic mucocutaneous disease that affects the skin and the oral mucosa,and presents itself in the form of papules,lesions or rashes. Lichen planusdoesn't involve lichens;the name refers to the appearance of affected skin.
The typical rash of lichen planus is well-described by the "4P's": well-defined pruritic, planar, purple, polygonal papules. Thecommonly affected sites are near the wrist and the ankle. The rash tends toheal with prominent blue-black or brownish discoloration that persists for along time. Besides the typical lesions, many morphological varieties of therash may occur. The presence of cutaneous lesions is not constant and may waxand wane over time. Oral lesions tend to last far longer than cutaneous lichenplanus 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 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.
The microscopic appearance of lichen planus is pathognomonic for thecondition
Lichen planus may also affect the genital mucosa vulvovaginal gingivallichen planus. It can resemble other skin conditions such as atopicdermatitis and psoriasis.
Rarely, lichen planus shows esophageal involvement, where it can presentwith erosive esophagitis and stricturing. It has also been hypothesized that itis a precursor to squamous cell carcinoma of the esophagus.
Clinical experience suggests that Lichen planus of the skin alone is easierto treat as compared to one which is associated with oral and genital lesions.