OSCE — apple-jelly nodules and neck sinuses: classify and treat cutaneous tuberculosis

Brief (to candidate)

A 40-year-old man from an endemic area has a chronic facial plaque with soft apple-jelly nodules on diascopy. A second patient has a broken-down cervical lymph node with draining sinuses. You have 8 minutes to classify cutaneous TB forms, plan investigations, start ATT, and explain tuberculids.

Candidate instructions

1. Name major clinicopathologic forms: lupus vulgaris, scrofuloderma, TB verrucosa cutis, orificial/miliary, tuberculids.
2. Link route of infection (exogenous / contiguous / haematogenous / hypersensitivity).
3. Plan biopsy + AFB/culture/PCR and systemic TB work-up.
4. Prescribe standard RIPE anti-TB therapy framework (6 months typical).
5. Explain that tuberculids are sterile hypersensitivity reactions requiring treatment of the focus.

Examiner checklist (mark each domain / 10)

Model key actions

• Diagnose lupus vulgaris and scrofuloderma phenotypes and start ATT pathway.^[1][5]
• Biopsy and mycobacterial work-up before or alongside treatment in non-emergency settings.^[1]
• Recognise tuberculids as sterile reactive patterns needing systemic TB control.^[8]

Common errors

• Treating chronic facial plaque as sarcoid/LE without mycobacterial consideration in endemic settings.
• Antibiotics alone for scrofuloderma without ATT.
• Assuming tuberculids need only topical therapy because AFB-negative.
• Missing Marjolin SCC risk in long-standing lupus vulgaris.
• Confusing paediatric scrofula from NTM adenitis (culture/PCR distinction; management may differ).