What are the causes of burning tongue (glossopyrosis)?

Causes of Burning Tongue (Glossopyrosis)

Burning tongue syndrome (glossopyrosis) is primarily caused by burning mouth syndrome (BMS), which can be primary (idiopathic) or secondary to various local and systemic conditions including oral candidiasis, mucosal lesions, haematological disorders, auto-immune disorders, and medication side-effects. 1

Primary Burning Mouth Syndrome

Primary BMS is considered a neuropathic disorder with no identifiable underlying cause:

• Peripheral nerve fiber disorder with central brain changes 1
• Altered sensory processing following small fiber neuropathic changes in the tongue 2
• Predominantly affects peri- and post-menopausal women 1
• Onset in women typically occurs 3-12 years after menopause 2
• Uncommon before age 30 (40 years for men) 2

Secondary Causes

Local Factors:

• Oral candidiasis 1
• Mucosal lesions 1
• Allergies to dental materials 3
• Denture-related lesions 4
• Local oral infections 4
• Chronic irritation from ill-fitting dentures or sharp teeth edges 5

Systemic Conditions:

• Haematological disorders 1
• Auto-immune disorders 1
• Nutritional deficiencies:
  • Iron deficiency 6
  • Vitamin B12 deficiency 6
  • Folic acid deficiency 6
  • Riboflavin deficiency 6
  • Niacin deficiency 6
  • Magnesium deficiency (particularly in glossopyrosis limited to the anterior tongue) 7
• Hormonal changes associated with menopause 4
• Diabetes mellitus 4
• HIV infection (may be an early symptom) 3
• Gastrointestinal disorders 3
• Neurological disorders 3

Medication-Related:

• Pharmacological side-effects 1
• Various medications can cause oral burning as a side effect 3
• Immune checkpoint inhibitor (ICI) therapy can cause oral dysesthesia with burning sensation 1

Psychological Factors:

• Depression 2, 3
• Anxiety 2
• Psychiatric conditions 3

Distinguishing Features

• Primary BMS typically presents with:

  • Burning sensation in tongue (especially tip and anterior two-thirds), lips, palate, and buccal mucosa 1, 2
  • Normal-appearing oral mucosa 1
  • Altered taste sensations (metallic taste) or diminished taste 2
  • Discomfort with acidic foods 2
  • Continuous symptoms, often with no clear trigger 1

• Secondary BMS presents with:

  • Similar burning sensations but with identifiable underlying cause 4
  • May have visible oral pathology depending on cause
  • May be limited to specific areas (e.g., anterior tongue in magnesium deficiency) 7

Red Flags Requiring Urgent Evaluation

• Persistent red sore on tongue beyond 2 weeks (rule out squamous cell carcinoma) 5
• Induration or fixation of lesions 5
• Unexplained bleeding 5
• Cervical lymphadenopathy 5
• Lesion growth despite treatment 5
• Persistent numbness or paresthesia 5
• History of tobacco or heavy alcohol use with persistent lesion 5

Diagnostic Approach

A thorough diagnostic workup is essential to distinguish between primary and secondary BMS:

1. Detailed history of symptoms (onset, duration, character, aggravating/relieving factors)
2. Examination of the entire oral cavity
3. Laboratory tests to rule out:
   • Nutritional deficiencies (iron, B12, folate, magnesium)
   • Diabetes
   • Autoimmune disorders
   • Hematological disorders
4. Biopsy for persistent lesions to rule out malignancy
5. Assessment for medication side effects

The diagnosis of primary BMS should only be established after all possible secondary causes have been ruled out 4.

By systematically evaluating these potential causes, clinicians can identify the underlying etiology of burning tongue and develop an appropriate treatment plan to address the patient's symptoms and improve quality of life.