The cause of fissured tongues is unknown, but the condition is possibly genetically inherited, according to WebMD. Fissured tongues often cluster in families, and can accompany conditions such as geographic tongue, Melkersson-Rosenthal syndrome and Down syndrome.
Tongue fissures manifest as cracks, clefts or grooves along the top and sides of the tongue, explains WebMD. Fissure depth varies, but can reach 6 millimeters deep, in some cases. The fissures affect only the tongue and can connect, creating sections in the tongue. Symptoms are rare, unless debris accumulates in the fissures, and individuals almost never require treatment. Tongue fissures afflict between 2 and 5 percent of the U.S. population.