What's causing these persistent yellow spots?

A 24-year-old woman presents with a one-year history of multiple asymptomatic firm skin-coloured-to-yellow papules around 2mm in diameter on her back.

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Professor Dedee Murrell is head of dermatology at St George Hospital, NSW, and conjoint professor at UNSW, Sydney.

This quiz was co-authored by Dr Niluka Paththinige, visiting dermatology fellow at St George Hospital, Sydney, and Yicong Liang, a