OSCE — recurrent oral aphthous ulcers: diagnosis, red-flag differentials, and stepwise therapy

Brief (to candidate)

A 24-year-old woman has recurrent painful oral ulcers for 3 years (3–5 episodes/year). Today she has two round ulcers on the non-keratinised buccal mucosa with erythematous halos. No genital ulcers, uveitis or GI symptoms reported. You have 8 minutes to classify the ulcers, exclude serious differentials, and plan management.

Candidate instructions

1. Classify minor vs major vs herpetiform aphthous ulcers by size, number and healing.
2. Differentiate from herpes, traumatic ulcer, Behçet, erythema multiforme, neutropenic/HIV-related ulcers.
3. Screen for systemic associations (coeliac, IBD, Behçet, haematinic deficiency, HIV when indicated).
4. Outline stepwise local then systemic therapy.
5. Give safety-net advice (persistent ulcer >2–3 weeks → biopsy/referral).

Examiner checklist (mark each domain / 10)

Model key actions

• Classify as recurrent minor aphthous stomatitis if small, non-keratinised, self-healing lesions without systemic features.^[1][5]
• Explicitly screen Behçet (genital, eye, skin pathergy) and haematinics/coeliac when recurrent.^[6][9]
• Start potent topical steroid preparation for oral use; escalate only if major/refractory.^[1]
• Biopsy/refer any solitary non-healing ulcer.

Common errors

• Calling every mouth ulcer herpes without site/vesicle history.
• Missing Behçet red flags (genital/ocular).
• Ignoring haematinic deficiency / coeliac work-up in frequent RAS.
• Leaving a non-healing ulcer without biopsy pathway.
• Using thalidomide without pregnancy prevention and neuropathy counselling.