Geographic tongue, also known by several other terms, is a condition of the mucous membrane of the tongue, usually on the dorsal surface. It is a condition affecting approximately 2–3% of the general population. It is characterized by areas of smooth, red depapillation (loss of lingual papillae) that migrate over time. The name comes from the map-like appearance of the tongue, with the patches resembling the islands of an archipelago. The cause is unknown, but the condition is entirely benign (importantly, it does not represent oral cancer), and there is no curative treatment. Uncommonly, geographic tongue may cause a burning sensation on the tongue, for which various treatments have been described with little formal evidence of efficacy.
Signs and symptoms
In health, the dorsal surface of the tongue is covered in tuft-like projections called lingual papillae (some of which are associated with taste buds), which give the tongue an irregular surface texture and a white-pink color. Areas of atrophy and depapillation (loss of papillae) characterize Geographic tongue, leaving an erythematous (darker red) and smoother surface than the unaffected areas. The depapillated areas are usually well-demarcated, and bordered by a slightly raised, white, yellow, or grey, serpiginous (snaking) peripheral zone. A lesion of geographic tongue may start as a white patch before the depapillation occurs. In certain cases, there may be only one lesion, but this is uncommon; the lesions will typically occur in multiple locations on the tongue and coalesce over time to form the typical map-like appearance. The lesions usually change in shape and size, and migrate to other areas, sometimes within hours. The condition may affect only part of the tongue, with a predilection for the tip and the sides of the tongue, or the entire dorsal surface at any one time. The condition goes through periods of remission and relapse. Loss of the white peripheral zone is thought to signify periods of mucosal healing. There are usually no symptoms other than the unusual appearance of the tongue, but in some cases, affected people may experience pain or burning when eating hot, acidic, spicy, or other foods (e.g., cheese, tomatoes, fruit). Where there is a burning symptom, other causes of a burning sensation on the tongue are considered, such as oral candidiasis.
Causes The cause is unknown. Geographic tongue does not usually cause any symptoms, and in those cases where there are symptoms, an oral parafunctional habit may be a contributory factor. Persons with parafunctional habits related to the tongue may show scalloping on the sides of the tongue (crenated tongue). Some suggest that hormonal factors may be involved, because one reported case in a female appeared to vary in severity in correlation with oral contraceptive use. People with geographic tongue frequently claim that their condition worsens during periods of psychological stress. Geographic tongue is inversely associated with smoking and tobacco use. Sometimes geographic tongue is said to run in families, and it is reported to be associated with several different genes. Studies show family association may also be related to similar diets. Some have reported links with various human leukocyte antigens, such as increased incidence of HLA-DR5, HLA-DRW6 and HLA-Cw6 and decreased incidence in HLA-B51. Vitamin B2 deficiency (ariboflavinosis) can cause several signs in the mouth, possibly including geographic tongue. However, other sources state that geographic tongue is not related to nutritional deficiency. Fissured tongue often occurs simultaneously with geographic tongue, and some consider fissured tongue to be an end stage of geographic tongue. In the past, some studies suggested that geographic tongue was associated with diabetes, seborrheic dermatitis, and atopy; however, newer research does not corroborate these findings. Others suggest allergy as a major factor, for example, to nickel sulphate. Geographic tongue and psoriasis co-occur at a rate that is higher than would be predicted by chance. Most people with geographic tongue do not develop psoriasis, and most people with psoriasis do not have geographic tongue. People who have both geographic tongue and psoriasis may have a greater severity of psoriasis and be less responsive to psoriasis treatment. Lesions that are histologically indistinguishable from geographic tongue may also be diagnosed in reactive arthritis (arthritis, uveitis/conjunctivitis, and urethritis).
Predisposing factors Geographic tongue (GT) is a lesion with an unknown origin. However, it has been reported more frequently in people with psoriasis, a history of allergies, asthma, and rhinitis. Studies have also suggested that psychological/psychiatric factors, diabetes mellitus, gastrointestinal diseases, and hematological disorders may predispose a person to GT; however, more studies with a larger cohort are needed to determine if GT could be an oral manifestation of a systemic disease. There is strong evidence to support a high prevalence of celiac disease and iron deficiency anemia in patients with GT. Oral candidiasis and dental cavities are commonly reported in patients with GT; however, this may be explained by saliva with a lower pH, which will promote the cariogenic process. The most common areas in which GT can be found include the lateral border of the tongue, followed by the anterior dorsum of the tongue and the ventral surface.
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