Atrophic glossitis is an inflammatory disease of the tongue that causes atrophy of the papillae (small projections on the surface of your tongue) found in the tongue structure. In this disease, the tongue appears red with a smooth surface. Causes of atrophic glossitis: Nutritional deficiency (iron deficiency, low B12 and folic acid levels and vitamin deficiencies), dry mouth, Sjögren's syndrome, fungal infection in the mouth, Celiac disease.

 

Source: http://www.kbb.org.tr