What is burning mouth syndrome in a smoker?

What is Burning Mouth Syndrome?

Burning mouth syndrome (BMS) is a chronic neuropathic pain disorder characterized by a persistent burning, stinging, or scalding sensation in the oral mucosa—most commonly affecting the tongue tip, lips, palate, and buccal mucosa—in the complete absence of visible mucosal lesions or clinical abnormalities. 1, 2

Pathophysiology and Clinical Features

BMS represents a disorder of peripheral nerve fibers with associated central nervous system changes, confirmed through neurophysiological testing, biopsies showing significantly lower density of epithelial nerve fibers, and functional MRI findings. 2 The condition predominantly affects peri- and post-menopausal women, with an estimated prevalence of 0.7-4.6% in the general population. 3

Key Clinical Characteristics

• Pain pattern: Continuous, spontaneous burning sensation described as if the mouth were "scalded or on fire," typically bilateral on the tongue tip. 2, 3
• Associated symptoms: Dry mouth (xerostomia), abnormal taste (dysgeusia), depression, and significantly impaired quality of life. 1, 2
• Hallmark diagnostic feature: Normal-appearing oral mucosa on examination despite severe subjective symptoms. 2

Critical Distinction: Primary vs. Secondary BMS

Primary (Idiopathic) BMS

• Occurs spontaneously without identifiable precipitating factors. 4
• Represents true neuropathic pain disorder. 2
• Diagnosis of exclusion only after ruling out all secondary causes. 2, 3

Secondary BMS (Must Be Excluded First)

Before diagnosing primary BMS, you must systematically exclude these secondary causes: 2

Local Oral Factors

• Oral candidiasis (diagnosed by scraping and KOH preparation). 2
• Traumatic ulceration from sharp dental edges, thermal burns, or chemical injury. 2
• Denture-related lesions. 3

Systemic Factors

• Hematological: Anemia, vitamin B12 deficiency, iron deficiency (check CBC, B12, ferritin, serum iron, TIBC). 2
• Autoimmune: Sjögren's syndrome, sicca syndrome. 2
• Endocrine: Thyroid disorders, particularly hyperthyroidism causing tongue erythema. 2
• Infectious: Post-herpetic neuralgia, scarlet fever, Kawasaki disease. 2

Medication Side Effects

• Various pharmacological agents can cause oral burning and must be reviewed. 2, 3

Neuropathic Causes

• Post-traumatic trigeminal neuropathic pain. 2

Special Considerations for Smokers

While smoking is not specifically identified as a primary cause of BMS in the guidelines, smokers presenting with oral burning require particularly careful evaluation to exclude:

• Chemical irritation from tobacco products (which would represent secondary burning, not true BMS). 2
• Mucosal lesions or premalignant changes that may cause burning sensations. 2
• Nutritional deficiencies more common in smokers (B vitamins, iron). 2

Important caveat: If mucosal abnormalities are present on examination, this is NOT burning mouth syndrome by definition—further investigation including possible biopsy is required. 2

Diagnostic Workup Algorithm

Step 1: Clinical History

• Onset timing, medication use, systemic diseases, recent dental procedures. 2
• Pain characteristics: continuous vs. intermittent, location, severity. 1

Step 2: Thorough Oral Examination

• Must show completely normal-appearing mucosa for primary BMS diagnosis. 2
• Identify any mucosal lesions, candidiasis, or traumatic factors. 2

Step 3: Laboratory Testing

• Complete blood count with differential. 2
• Vitamin B12 levels. 2
• Iron studies (ferritin, serum iron, TIBC). 2
• Consider thyroid function tests. 2

Step 4: Additional Testing if Indicated

• Qualitative sensory testing if neuropathic etiology suspected. 2
• Biopsy only if mucosal abnormalities present or diagnosis uncertain. 2

Common Pitfalls to Avoid

• Failing to exclude secondary causes before diagnosing primary BMS—this is the most critical error, as treatment approaches differ fundamentally. 2, 3
• Inadequate reassurance—patients must understand this condition will not progress to cancer or other serious disease, as anxiety significantly worsens symptoms. 1
• Ordering IgE levels routinely—these are nonspecific and should only be checked if specific allergic conditions are suspected. 2
• Assuming visible oral changes are compatible with BMS—by definition, BMS presents with normal-appearing mucosa. 2

Prognosis and Patient Counseling

• Treatment failures are common in BMS management. 1
• The condition is chronic and may require long-term management strategies. 1
• More than one-third of patients may have multiple concurrent contributing factors. 3
• Emphasize that the condition will not worsen or transform into malignancy—this reassurance is crucial for reducing patient anxiety. 1