Explaining a suspected fungal toenail and the confirm-before-treat principle — OSCE

Candidate instructions (8-minute station)

You are the paediatric registrar in clinic. A 9-year-old boy has an 18-month history of a thickened, yellow, crumbly left great toenail with subungual hyperkeratosis and distal onycholysis. His father has tinea pedis and a thickened toenail. The family has come expecting tablets to clear it quickly. ^[4]

Your tasks are: ^[1]

1. Explain the likely diagnosis — a fungal nail infection or onychomycosis — in plain language, and how his father's foot infection is linked. ^[4]
2. Explain why a test (a nail sample for mycology) must come before any tablets, and what that test involves. ^[4]
3. Outline the treatment ladder once confirmed — topical for limited disease, weight-based oral terbinafine for extensive disease — and set the expectation about how long a toenail takes to look normal. ^[4]
4. Explain the prevention (treating the household contact) and name the red flags in a disordered nail that would bring the child back sooner. ^[1]

You are not expected to start systemic therapy in this station — the confirm-before-treat principle means the test comes first. ^[4]