Irregular denuded erythematous patches on the surface of the tongue, which give a map-like appearance and which can vary on a daily basis. It is caused by filiform papilla depapillation on the dorsal and lateral aspects of the tongue; the underlying connective tissue is infiltrated by mixed chronic inflammatory cells. The condition may be persistent and uncomfortable, although most lesions are asymptomatic. The cause is unknown although stress, allergies, and vitamin B, iron, and zinc deficiency have been implicated. See also glossitis.