New perspectives on the dynamic behaviour of oral lichen planus.

Lichen planus, a chronic inflammatory disease that affects the skin and mucous membranes, is one of the most frequent dermatological disorders of the oral cavity. The prevalence of oral lichen planus ranges from 0.2% to 4%. The triggering factors remain unknown. Oral lichen planus can be considered to be a chronic disease of long duration with a dynamic evolution and frequent changes in clinical appearance. Three successive active stages can be distinguished, without sharp limits between them: an initial stage; a protracted intermediate stage with alternate periods of variable activity and quiescence, which carries a progressively increasing risk of malignant transformation; and a late stage that often ends in a clinically little-known, inactive cicatricial post-lichen stage, which does not respond to steroid treatment but retains the same risk.