Lichen planus is a chronic dermatosis which may affect both skin and mucosa.  Frequently the oral lesions are unique or precede the cutaneous ones.  It presents either tipically or atipically.  Tipically we see intercrossing white lines that give the appearance of a weave or net (arboriform);  the color of the mucosa in the lesion´s area may be normal or turn reddish.  Usually they are asymptomatic.  The causes of lichen planus are unknown and in some patients the lesions may disappear spontaneously.