Lichen planus is a chronic inflammatory dermatosis, the basic lesions of which consist of small polygonal, flat, glistening, red or bluish red papules, some slightly dimpled, which tend to coalesce and form irregular, raised patches. Papules which are first about the size of a pinhead often increase by peripheral growth. Healing may proceed in the center or at one edge of a large papule or of a small patch and result in the formation of rings or crescenting figures. New papules often appear along a scratch. On a fully developed patch is to be made out a network of delicate gray stretch marks, characteristic of the disease. While the earliest rash is sometimes a rose-red color, the larger, older lesions nearly always shade into a violaceous or purple hue. Where the eruption has disappeared, a brownish pigmentation is left to be slowly absorbed. Rarely there is atrophy of the skin.