OSCE — Pellagra (niacin/vitamin B3 deficiency)

Brief (to candidate)

You will assess a patient with a presentation consistent with Pellagra (niacin/vitamin B3 deficiency).
You have 8 minutes to take a focused history, outline examination, investigations, and management including red flags.

Clinical context

Pellagra is a systemic disease caused by deficiency of niacin (vitamin B3) or its amino acid precursor tryptophan, classically presenting with the '3 Ds': dermatitis (a sharply demarcated photosensitive rash on sun-exposed skin including Casal's necklace), diarrhoea, and dementia — with death as the untreated 4th D. Causes span dietary deficiency (maize/sorghum-based diets), alcoholism, malabsorption, Hartnup disease (impaired tryptophan transport), carcinoid syndrome (tryptophan diversion to serotonin), and isoniazid therapy (vitamin B6 antagonism). Tryptophan converts to niacin (~60 mg to 1 mg) via the kynurenine pathway, requiring B6, B2, and B1. Treatment is oral nicotinamide (niacinamid

Candidate tasks

1. Clarify onset, severity, associated features, and red-flag symptoms.
2. State focused examination priorities.
3. List first-line investigations and any named score/criteria.
4. Give immediate resuscitation steps.
5. Outline definitive management with doses/routes where standard.
6. Name complications and disposition (ward / HDU / theatre / discharge safety-net).
7. Mention one special-population modifier (pregnancy, child, elderly, CKD).

Examiner checklist

Model outline

Lead with the working diagnosis and life threats. Resuscitate before definitive tests when unstable. Use guideline-standard therapy with named agents and doses. Document escalation criteria and follow-up. A safe candidate is specific, structured, and never delays critical care for non-urgent imaging.^[2]