Fissured tongue is a condition frequently seen in the general population that is characterized by grooves that vary in depth and are noted along the dorsal and lateral aspects of the tongue, as shown in the image below.
Although a definitive etiology is unknown, a polygenic mode of inheritance is suspected because the condition is seen clustering in families who are affected. Patients are usually asymptomatic, and the condition is initially noted on routine intraoral examination as an incidental finding.  Fissured tongue is also seen in Melkersson-Rosenthal syndrome  and Down syndrome and in frequent association with benign migratory glossitis (geographic tongue). Fissured tongue and geographic tongue have been reported in association with chronic granulomatous disease. 
Melkersson-Rosenthal syndrome is a rare condition consisting of a triad of persistent or recurring lip or facial swelling, intermittent seventh (facial) nerve paralysis (Bell palsy), and a fissured tongue. The etiology of this condition is also unknown. The orofacial swelling usually manifests as pronounced lip enlargement. It may or may not affect both lips, and it may be tender or erythematous. Histologic examination of this tissue exhibits characteristic noncaseating granulomatous inflammation. Therapy for these lesions is often intralesional steroid injections.  The facial paralysis is indistinguishable from Bell palsy, and it may be an inconsistent and intermittent finding with spontaneous resolution. The presence of fissured tongue in association with these other features is diagnostic of the condition.
Fissured tongue affects only the tongue and is a finding in Melkersson-Rosenthal syndrome, which consists of a triad of fissured tongue, granulomatous cheilitis, and cranial nerve VII paralysis (Bell palsy). [5, 6]
Overall, the prevalence of fissured tongue within the United States has been reported to range from 2-5% of the population.
No predilection for any particular race is apparent in fissured tongue.
Some reports have shown a slight male predilection for fissured tongue.
Although fissured tongue may be diagnosed initially during childhood, it is diagnosed more frequently in adulthood. The prominence of the condition appears to increase with increasing age.
Fissured tongue is a totally benign condition and is considered by most to be a variant of normal tongue architecture. When seen in association with Melkersson-Rosenthal syndrome, the morbidity is due not to the fissured tongue but is secondary to the granulomatous inflammation of the lips/facial soft tissues and facial paralysis.
Inform patients that fissured tongue is a frequent finding and no specific therapy is required, aside from that necessary to treat the manifestations of Melkersson-Rosenthal syndrome, if present.