Approach to rash in infants and children — viva

Opening (candidate frames the problem)

Examiner: A 14-month-old, 12 hours of fever, irritable, rash over the lower limbs. Talk me through your assessment. [1]

Model answer: I assess sick-or-well first. I take the paediatric assessment triangle and vital signs, because an unwell child with a rash is an emergency regardless of the rash itself. I fully undress the child, examine the whole skin including mucosae, palms and soles, and palpate the lesions - specifically testing blanching with a glass slide. [1]

Examiner (probe): Why blanching first? [7]

Model answer: Because blanching is the single highest-yield bedside test. Erythema and wheals blanch because they are vascular; purpura does not, because the blood is outside the vessel. A non-blanching purpura in an unwell febrile child is meningococcaemia until proven otherwise. [7]