Definition Lichen planus is a relatively common chronic inflammatory disease of the oral mucosa and skin.
Etiology Although the cause is not well known, T cell-mediated autoimmune phenomena are involved in the pathogenesis .
Clinical features White papules that usually coalesce, forming a network of lines (Wickman’s striae), are the characteristic oral lesions of the disease. Six forms of the disease are recognized in the oral mucosa, classified according to frequency: the common (reticular, erosive, Figs. 4, 5); the less common (atrophic, hypertrophic, Fig. 6); and the rare (bullous, pigmented, Fig. 7). Middle-aged individuals are more commonly affected (the ratio of women to men ratio is 3 : 2). The buccal mucosa, tongue, and gingiva are the sites of predilection. The skin lesions characteristically appear as polygonal purple, pruritic papules, usually affecting the flexor surfaces of the extremities. The glans penis and nails may also be affected. The disease can usually be diagnosed on clinical grounds alone. The prognosis of lichen planus is usually good, and malignant transformation (particularly of the erosive form) remains controversial.
Fig. 4 Lichen planus of the buccal mucosa reticular form
Laboratory tests Histopathological examination is very helpful. Direct immunofluorescence can also be used, although the features are not specific.
Differential diagnosis Discoid lupus erythematosus, candidiasis, graft-versus-host disease, geographic tongue, leukoplakia, erythroplakia, cicatricial pemphigoid, pemphigus, bullous pemphigoid.
Treatment No treatment is needed in asymptomatic lesions. Topical steroids (ointment in Orabase, intralesional injection), may be helpful. Systemic steroids in low doses can be used in severe and extensive cases. The topical use of antiseptic mouthwashes should be avoided.
Fig. 5 Lichen planus, papular and reticular forms, of the buccal mucosa.
Fig. 6 Lichen planus of the dorsum of the tongue hypertrophic form.
Fig. 7 Lichen planus, pigmented form, of the buccal mucosa.
