Bonnie is a 21-year-old accounting student with a two-month history of persistent erythematous patches on both thighs.

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<p>Bonnie is a 21-year-old accounting student with a two-month history of persistent erythematous patches on both thighs.</p><p>These are not symptomatic, but she is concerned by their appearance and persistence.</p><p>She has tried using a regular low-irritant emollient, to no effect.</p><p>Bonnie is otherwise well, with no systemic symptoms, or other skin or joint complaints. She has no past history of note, no allergies and takes no regular medications.</p><p>She studies long hours sitting at a desk and often holds a vacuum flask filled with coffee or herbal tea between her legs.</p><p>On examination, vital signs are within normal limits. There are symmetrical, dark red, reticular patches on both inner thighs.</p><p>These lesions have indistinct margins, do not blanch, and are accompanied by mild localised scaling. No other regions are affected.</p>

Dr Kate Kelso is a GP and medical editor at Australian Doctor.