What causes geographical tongue?

Causes of Geographic Tongue

Geographic tongue is primarily caused by a combination of genetic predisposition, immune dysregulation, nutritional deficiencies, and allergic reactions, with no single definitive cause identified.

Etiology and Risk Factors

Geographic tongue (benign migratory glossitis) is characterized by irregular, map-like patches on the tongue surface due to loss of filiform papillae. Several factors have been implicated in its development:

Immune-Related Factors

• Psoriasis association: Geographic tongue shares histological similarities with psoriasis, suggesting a possible common pathophysiological mechanism 1
• Inflammatory response: The condition involves nonspecific inflammation of the tongue epithelium 2

Nutritional Deficiencies

• Zinc deficiency: Patients with geographic tongue have significantly lower levels of salivary zinc compared to healthy individuals 3
• Other potential deficiencies: Iron and vitamin B12 have been suggested as contributing factors, though research shows their serum and salivary levels may not differ significantly between affected and unaffected individuals 3

Allergic and Dietary Triggers

• Food allergies: Spicy foods, particularly chili, can trigger or exacerbate geographic tongue in susceptible individuals 4
• Allergic tendency: Elevated IgE levels and positive skin prick tests to specific allergens have been documented in some patients 4

Other Associated Factors

• Age-related: More prevalent among young individuals 2
• Genetic factors: Family history may play a role in susceptibility 2
• Emotional stress: Psychological factors may trigger or worsen episodes 2
• Hormonal disturbances: Endocrine changes may influence manifestation 2
• Coexisting conditions: May occur alongside fissured tongue, diabetes mellitus, gastrointestinal diseases, and burning mouth syndrome 2

Biological Mechanism

The characteristic migratory pattern of geographic tongue lesions suggests it functions as a reaction-diffusion system, with propagating waves across the curved surface of the tongue 5. This explains the dynamic nature of the lesions that change in shape and location over time.

Clinical Implications

For symptomatic patients with geographic tongue:

1. Identify and avoid triggers: Particularly food allergens like chili if demonstrated by testing 4
2. Consider nutritional supplementation: Especially zinc, which shows decreased levels in affected individuals 3
3. Manage symptoms: Topical treatments like benzydamine hydrochloride mouthwash can provide relief 4
4. Allergy testing: May be beneficial in cases where food triggers are suspected 4

Monitoring and Prognosis

• Geographic tongue typically follows a pattern of remission and exacerbation
• Most cases have good prognosis and are self-limiting
• Severity can be assessed using the Geographic Tongue Area and Severity Index (GTASI) 4
• Pain levels can be monitored using numerical rating scales 4

Understanding these various contributing factors is essential for effective management of geographic tongue, though further research is needed to fully elucidate the precise etiology of this condition.