A 49-year-old man presents with several months of pruritic rash and progressive excoriated nodules affecting his torso and upper and lower limbs.

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

This article was co-authored by Dave Wi, a fourth-year medical student at UNSW and Dr Anna Wilson, a dermatology research fellow at St George Hospital.