Maureen is an 84-year-old who presents with a three-week history of a rapidly growing, tender lesion on the ring finger of her left hand (see figure 1).

She is right-handed. She is not aware of any preceding trauma or injury to the site.

Maureen is otherwise reasonably fit and well. She has a history of ischaemic heart disease for which she takes regular aspirin, a statin and an ACEI, with which she is adherent.

On examination the lesion appears as a domed, erythematous papule with a central keratin plug.