Median Rhomboid Glossitis
This condition is a classic developmental disorder of the tongue. It is a failure of the developmental apparatus during the organogenesis of the fetus. A structure called "tuberculum impar" is supposed to withdraw when the two halves of the tongue come close to each other during development.
When this does not happen, the structure gets trapped in between the two halves of the tongue, thereby creating an area, which looks like a bald patch on it. Median Rhomboid Glossitis has also been strongly linked with the fungal infection caused by Candida albicans, where the tongue has an ovoid patch just before the entry into the esophagus. Sometimes a flat-raised area can also be discerned. This condition is reportedly thrice as common in men as in women. The exact cause for this occurrence is not known, although hormonal links have been suggested.
There is no known treatment for MRG, though doctors have tried to administer anti-fungal agents with mixed results.