As of 2015, the exact cause of fissured tongue is unknown, and the condition is benign, the American Academy of Oral Medicine states; however, some congenital cases develop when the tongue fails to fuse completely before birth, the National Organization for Rare Disorders explains. Fissured tongue is also associated with Down syndrome and Melkersson-Rosenthal syndrome. Research suggests that some cases are hereditary and linked to geographic tongue, a condition that causes the formation of smooth red patches.
Some doctors argue that fissured tongue without geographic tongue is a normal biological variant, the National Organization for Rare Disorders states. In other cases, the condition is linked to infection or poor malnutrition.
Shallow or deep grooves on the upper surface of the tongue characterize fissured tongue, according to the American Academy of Oral Medicine. The person may have a single furrow or multiple fissures, and some cases include a fissure along the tongue's center. Fissured tongue affects roughly 5 percent of the U.S. population, and the condition is more common and pronounced in people of advanced age. Although the condition is harmless, good oral hygiene is necessary to prevent food debris from collecting in fissures. Dentists recommend regular tongue cleansing to clear the fissures and to reduce the risk of bad breath or irritation.