Studies have also suggested that psychological/psychiatric factors, diabetes, gastrointestinal diseases and haematological disorders may predispose 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 anaemia in patients with GT. Oral candidiasis and caries are commonly reported in patients with GT, however this can be explained by saliva of a lower pH which will promote the cariogenic process. 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 ventral surface. Diagnosis
Diagnosis of Geographic Tongue (GT) mainly relies on clinical, intraoral findings. As GT is usually asymptomatic in the mouth it does not require treatment. A differential diagnosis between oral candidiasis and GT, two similar looking conditions, can be established through a careful and thorough examination. GT is a keratotic lesion which can be described as a round or irregular shaped white plaque, cannot be scraped off and is normally self-resolving. These lesions are known to reoccur within variable periods. Although rare, cytological techniques and biopsies can be done to aid in a clinical diagnosis. The cytological description can define the disease due to its inflammatory characteristics, with its main characteristic being nuclear demarcation. Furthermore, it is important to be aware that GT may be related to other extraoral and intraoral conditions.
The condition often starts in childhood, sometimes at an early age, but others report that the highest incidence occurs in the over 40 age group. Females are sometimes reported to be more commonly affected than males, in a 2:1 ratio, although others report that the gender distribution is equal. Clinical Implications
Psoriasis
A recent study has proven the link between geographic tongue (GT) and psoriasis - the presence of geographic tongue can be a predictor of psoriasis. Clinical manifestation of GT and psoriasis can be histologically similar, however a genetic link between the two has been pathogenically identified. Patients with generalised pustular psoriasis and GT both exhibit the c.115 +6T >C mutation in the IL36RN gene. Patients who have GT have been shown to experience a greater severity of psoriasis and have a less positive response to treatment. Oral Manifestations in Patients with COVID-19
Many articles including case reports, case-series and cross-sectional studies have been done since the recent outbreak of COVID-19, causing a global pandemic. These studies have shown that approximately 20% of patients with COVID-19 can present with mucosal manifestations in their oral cavities, including geographic tongue. Geographic tongue is also thought to appear alongside the onset of the regular symptoms of COVID-19. Interleukin-6 (IL-6) is known to be an important biomarker in patients with COVID-19 in relation to a cytokine storm where too many inflammatory cells which have a detrimental effect on organ systems throughout the body. Geographic tongue is associated with elevated levels of IL-6, which possibly helps explain its presentation on confirmed COVID-19 patients.