What do I assess in a patient with a canker sore?

Assessment of Canker Sores (Recurrent Aphthous Stomatitis)

For any oral ulcer persisting beyond 2 weeks or not responding to 1-2 weeks of empiric treatment, biopsy is mandatory to exclude malignancy and serious systemic disease. 1

Initial Clinical Assessment

History Taking

Duration and Pattern

• Document the exact date when the ulcer first appeared and track its progression 1
• Determine if this is a first occurrence or recurrent pattern (RAS typically begins in second decade, peaks in third decade) 2, 3
• Ask about frequency of recurrence and duration of individual lesions 4

Pain and Functional Impact

• Assess pain severity and impact on eating, drinking, and speaking 1
• Note if pain is disproportionate to the size of the lesion 1

Associated Symptoms

• Ask about fever, malaise, or prodromal illness 1
• Inquire about genital ulcers (suggests Behçet's disease) 3, 4
• Ask about eye symptoms including pain, redness, or vision changes (posterior uveitis in Behçet's) 3
• Document gastrointestinal symptoms: abdominal pain, diarrhea, or blood in stool (Crohn's disease) 1
• Ask about skin lesions on hands, feet, or elsewhere 5, 6
• Inquire about joint pain or swelling 6

Medication and Exposure History

• Record ALL medications taken in the previous 2 months, including over-the-counter and complementary therapies, with exact start dates 1
• Document any recent medication changes or brand switches 1
• Ask about previous drug allergies and reaction types 1

Risk Factors and Triggers

• Family history of recurrent oral ulcers (genetic predisposition) 1, 3
• Recent trauma to the area (biting, dental work, sharp teeth) 1, 2
• Dietary triggers: gluten, tomatoes, citrus fruits, spicy foods 5, 2, 4
• Stress, hormonal changes, or recent illness 4
• Smoking history (protective in RAS but risk factor for malignancy) 4

Medical History

• History of tuberculosis or exposure 1
• HIV status or risk factors 1
• Diabetes or hyperglycemia 1
• Inflammatory bowel disease 1
• Immunosuppression or immunocompromising conditions 5
• Blood disorders including anemia or neutropenia 1, 4

Physical Examination

Ulcer Characteristics

• Location: Note if on non-keratinized mucosa (typical for RAS: buccal mucosa, labial mucosa, tongue, soft palate, floor of mouth) versus keratinized surfaces 3
• Number: Single versus multiple ulcers 1
• Size and morphology:
  • Minor aphthae: <1 cm, round/oval, shallow 3
  • Major aphthae: >1 cm, deeper, may scar 3
  • Herpetiform: multiple small ulcers 3
• Borders: Well-circumscribed with erythematous halo (typical RAS) versus irregular, raised, or indurated edges (concerning for malignancy) 1, 3
• Base: Yellow or gray pseudomembrane (typical RAS) versus necrotic, granular, or stellate appearance 1
• Surrounding tissue: Look for inflammation, induration, or fixation to underlying structures 1

Extraoral and Systemic Examination

• Examine skin for vesicles, bullae, or rash on hands and feet (hand-foot-mouth disease) 5, 6
• Check for genital ulcers 1, 3
• Assess eyes for conjunctivitis, uveitis, or other inflammation 1, 3
• Palpate cervical lymph nodes for enlargement or tenderness 1
• Examine for pathergy (skin hyperreactivity to minor trauma in Behçet's) 6

Intraoral Examination

• Inspect all mucosal surfaces systematically 1
• Look for other lesions with different morphology (may require multiple biopsies) 1
• Check teeth for sharp edges, decay, or trauma sources 1
• Assess oral hygiene status 1

Laboratory Investigations

Mandatory Pre-Biopsy Blood Work (before any biopsy for ulcers >2 weeks) 1, 7

• Full blood count (screen for anemia, leukemia, neutropenia) 1, 7
• Coagulation studies (PT/INR, aPTT) to exclude biopsy contraindications 7
• Fasting blood glucose (hyperglycemia predisposes to fungal infections) 1, 7
• HIV antibody 1, 7
• Syphilis serology (RPR/VDRL and treponemal test) 1, 7

Additional Testing Based on Clinical Suspicion

• Vitamin B12, folate, and iron studies if anemia or nutritional deficiency suspected 7, 4
• Serum specific antibodies (Dsg1, Dsg3, BP180, BP230) if bullous disease suspected 1, 7
• 1-3-β-D-glucan and galactomannan if invasive fungal infection suspected (diabetic or immunocompromised patients) 1, 7
• Tuberculin skin test (PPD) or interferon gamma release assay (TB-IGRA) if TB suspected 7

When to Perform Biopsy

Absolute Indications 1, 7

• Any ulcer persisting >2 weeks without clear diagnosis
• Ulcer not responding to 1-2 weeks of appropriate treatment
• Atypical features: irregular borders, induration, fixation to underlying tissue
• Single large ulcer (>1 cm) in patient >40 years old
• Ulcers with different morphological characteristics (require multiple biopsies) 1

Biopsy Technique Considerations

• Include ulcer margin and adjacent normal tissue 1
• For suspected bullous disease, obtain separate specimen for direct immunofluorescence (DIF) from perilesional tissue 7
• Avoid biopsy of necrotic center alone 1

Imaging Studies

Indicated When:

• Maxillofacial CT if ulcer near bone to assess for destruction 7
• Chest CT if tuberculosis, fungal infection, or paraneoplastic syndrome suspected 7
• Nasal CT and nasopharyngoscopy if nasal symptoms present 7

Red Flags Requiring Urgent Evaluation

• Ulcer >2 weeks duration 1, 6
• Indurated or fixed ulcer 1
• Painless ulcer (malignancy often painless initially) 1
• Unilateral cervical lymphadenopathy 1
• Constitutional symptoms: fever, weight loss, night sweats 1
• Respiratory symptoms: cough, dyspnea, hemoptysis 1
• Widespread erosions with positive Nikolsky sign (pemphigus) 6
• Severe oral involvement preventing adequate hydration 5

Common Pitfalls to Avoid

• Do not assume all recurrent oral ulcers are benign RAS without proper assessment 1
• Do not delay biopsy beyond 2 weeks for persistent ulcers 1
• Do not biopsy without checking coagulation studies first 7
• Do not miss associated systemic symptoms that suggest Behçet's, Crohn's, or other systemic disease 3, 4
• Do not forget to ask about ALL medications including over-the-counter products 1
• Do not overlook nutritional deficiencies as correctable causes 4