First described by Rayer in 1831, geographic tongue is a benign chronic relapsing recurring inflammatory condition of the oral cavity of unknown etiology.[1] It can also be referred to as benign migratory glossitis, erythema migrans, annulus migrans, and a wandering rash of the tongue.[1][2][3][4] It usually manifests as asymptomatic erythematous and migratory circinate patches that give its characteristic appearance of a map.[1][5] Depending on the individual, the lesion persists for a period of several days to weeks and then disappears and reappears in a different location.[1][6] Lesions usually occur on the lateral and dorsal aspects of the tongue; however, extra-lingual lesions can be seen on lips, labial and buccal mucosa and floor of the mouth.[1][2][4] Geographic tongue has been associated with other conditions leading to different theories of the pathogenesis of the disorder.

The etiology of geographic tongue remains largely unknown; however, a few theories have been proposed.[1][2] Psychosomatic and hereditary factors have been suggested to have a role in the etiology of geographic tongue.[2] Redman et al. showed a higher prevalence of geographic tongue in mentally ill patients.[7] Ebrahimi et al. showed that decreasing stress could help heal lesions in geographic tongue, further demonstrating an association between stress and geographic tongue[2]. A possible role of familial and hereditary factors has been suggested.[1][4] Redman et al. showed that geographic tongue was more prevalent in first degree relatives than in the control group (14.4% vs. 4%). An increased prevalence of geographic tongue in parents and siblings was significantly higher than in the general population. A polygenetic inheritance model has been proposed regarding the etiology of this disorder.[8]

Geographic tongue usually begins in childhood and has an overall global prevalence of approximately 1% to 2.5% of the population. The prevalence in the pediatric population ranges from 0.37% to 14.3%. The greatest prevalence occurs in the age group of 20 to 29 years of age at about 39.4%. Geographic tongue has a slightly greater predilection for women than men.[1][2]

The pathogenesis of geographic tongue remains unknown to this date; however, several theories have been proposed.[1] Several studies have shown a link between asthma, eczema, hay fever, allergic rhinitis, patients with higher levels of immunoglobulin E, and geographic tongue.[2][4] Marks and Tait et al. observed a positive association between geographic tongue and asthma and atopy, further suggesting similar pathogenesis for both disease entities.[2] Jainkittivong et al. showed that geographic tongue was more commonly seen in patients with allergies to drugs, food, or others.[9] Miloglu et al. showed that 24.1% of patients with geographic tongue had atopy or allergic disease concurrently.[10]

Due to clinical, histopathological, and immunohistochemical similarities between geographic tongue and psoriasis, some experts believe geographic tongue to be an oral manifestation of psoriasis.[2] A strong association with human leukocyte antigen (HLA)–Cw6 and a weak association with HLA-B13 has been reported in both geographic tongue and psoriasis.[2] This association is controversial as some have stated strong evidence is lacking and that geographic tongue and psoriasis may rather occur coincidentally also given the fact that there is a large percentage of healthy patients with geographic tongue.[4]

Hormones have also been proposed to play a role in the pathogenesis of geographic tongue.[1][2][4] Wysocky and Daley found a fourfold increase in the incidence of geographic tongue and diabetes.[11] However, on the contrary, studies have also shown no significant correlation between geographic tongue and insulin-dependent diabetes mellitus.[2]

 Oral contraceptive pills that cause hormonal fluctuation have been associated with geographic tongue, further indicating a possible hormonal role in this disorder.[2] Angiogenesis inhibitors have also been reported to induce geographic tongue possibly.[2]

Vitamin D, B6, B12, folic acid, iron, and zinc deficiency have also been proposed to play a role in the pathogenesis of geographic tongue.[2][4][12]

Tobacco use has been shown to play a protective role in the pathogenesis of geographic tongue.[2] The incidence of geographic tongue seems to be less in smokers than compared to nonsmokers, possibly due to increased keratinization and decreased TNF-a, IL-1, and IL-6 by macrophages via activation of nicotinic receptors.[12]

Microscopic examination of the white area of geographic tongue shows subepithelial infiltrates with a predominance of neutrophils forming microabscess, epithelial acanthosis associated with an elongation of the rete ridges, acantholysis, parakeratosis, glycogen deposits in the epithelial cells, and exfoliation of necrotic cells in the surface layer. The histopathology of the erythematous area of the lesion may show mononuclear subepithelial infiltrate (predominantly CD4+ T-lymphocytes), suprapapillary hypertrophy, and vascular ectasia.[1][2][12] Under electron microscopy, two types of pathology can be seen.[2] Loss of filiform papillae can be seen under the erythematous area, while necrotic cells can be seen under the white region of geographic tongue.[12]