This strange disease, also known as benign migratory glossitis, is very little understood. The so-called 'geographic tongue' syndrome is characterised by a change in the appearance of the tongue of those affected, making the tongue take on the appearance of a map.With unknown causes, this condition is incurable today but researchers at the Weizmann Institute have just lifted a bit of the mystery surrounding the condition. What is 'geographic tongue'?The affected tongue looks like a 'geographic map' because of the uneven red patches that appear on its surface, which are surrounded by a whitish outline. The shape of the 'map' varies from day to day, and the red areas are characterised by the appearance of inflammation of the so-called filiform taste buds.Although it is benign, geographic tongue alters the sense of taste of those affected. Some have a metallic taste in their mouths, but the syndrome can also be painful; cracks can appear on the tongue, creating a burning sensation when acidic foods are eaten. It is estimated that only 2% of the world's population is affected by this incurable condition.Although this is a chronic condition, it can appear and disappear for those who are affected, adding to the mystery surrounding it. Only some symptoms can be treated to reduce the discomfort and embarrassment that can stem from having it.Several types of geographic tonguePhysicians at the Weizmann Institute in Israel, however, have just solved part of the mystery surrounding this syndrome. By studying the dynamics of the inflamed plaques, i.e. their shape and how they evolve over time, the researchers have managed to show that there are at least two types of geographic tongue.In the first form, the inflammation appears in small circles that become larger and larger, while maintaining their circular aspect. Just like a fire that can’t return to an area it has already burnt up until the vegetation grows back, the red patches don’t reappear on areas that it has already touched. On the contrary, the second type of geographic tongue is characterised by repeated inflammation of the same areas, which can persist over long periods of time.With the latter, the patches appear in the form of spirals, which sometimes extend to areas of the tongue that are still healing. Researchers hope that their results will help to better understand this strange disease. Doctors will also be able to use their results to find out what form of geographic tongue is affecting their patients, and thus how to better assess their situation.