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.
The differential diagnosis includes oral lichen planus, erythematous candidiasis, leukoplakia, lupus erythematosus, glossitis, and chemical burns. Atrophic glossitis is usually distinguished from benign migratory glossitis on the basis of the migrating pattern of the lesions and the presence of a whitish border, features which are not present in atrophic glossitis, which instead shows lesions which enlarge rather than migrate. Rarely, blood tests may be required to distinguish from glossitis associated with anemia or other nutritional deficiencies. Since the appearance and the history of the condition (i.e. migrating areas of depapillation) are so striking, there is rarely any need for biopsy. When biopsy is taken, the histopathologic appearance is quite similar to psoriasis:

Hyperparakeratosis. Acanthosis. Subepithelial T lymphocyte inflammatory infiltrate. Migration of neutrophilic granulocytes into the epithelial layer, which may create superficial microabscesses, similar to the Munros microabscesses described in pustular psoriasis. Classification
Geographic tongue could be considered to be a type of glossitis. It usually presents only on the dorsal 2/3 and lateral surfaces of the tongue, but less commonly an identical condition can occur on other mucosal sites in the mouth, such as the ventral surface (undersurface) of the tongue, mucosa of the cheeks or lips, soft palate or floor of mouth; usually in addition to tongue involvement. In such cases, terms such as stomatitis erythema migrans, ectopic geographic tongue, areata migrans, geographic stomatitis, or migratory stomatitis are used instead of geographic tongue.