Contact dermatitis — branching viva

Examiner opening (Examiner)

You are the general paediatric registrar in the outpatient clinic. A nine-year-old girl with known atopic eczema is referred because an intensely itchy, well-demarcated band of eczema around her umbilicus keeps coming back whenever she wears her favourite jeans, despite her usual eczema creams. Talk me through your assessment and your working diagnosis. ^[5]

Exemplar opening (Candidate)

This is a classic distribution clue. A recurrent, intensely itchy, well-demarcated periumbilical dermatitis that tracks her clothing is allergic contact dermatitis to nickel from the metal button of her jeans until proven otherwise, on a background of atopic eczema. The key features are the recurrence at the same anatomical site, the clear relationship to a metal contact, the itch rather than soreness, and the failure of her usual eczema therapy — all of which point away from a simple flare of her atopic eczema. I will take a careful exposure history covering her jewellery, belt buckles and buttons, examine the whole skin including the earlobes for any similar reaction, and arrange patch testing to confirm the allergen. ^[5]