Sometimes geographic tongue is said to run in families, and it is reported to be associated with several different genes, though studies show family association may also be caused by 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, although 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 research 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, e.g. to nickel sulphate. Some studies have reported a link between geographic tongue and psoriasis, although 90% of children who are diagnosed with geographic tongue do not develop psoriasis. Again however, modern research studies do not support any link between psoriasis and geographic tongue. 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, history of allergies, asthma and rhinitis.
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.