A chronic localised itch on the back

Case history

A 67-year-old man presented complaining of a burning itching sensation on the same area of his back for the last 12 years. He reported that he was frequently scratching the area or rubbing it on doorjambs, which gave temporary relief. He had type 2 diabetes (controlled with diet) and hypertension (controlled with enalapril) but was otherwise well. No treatment had helped, and he was applying the high potency corticosteroid betamethasone dipropionate ointment, ‘for something to do’.

On examination, there was a brownish, lichenified (thickened), palm-sized area on his lower back to the left of the midline (Figures 1 and 2). There were no rashes elsewhere. Sensory testing showed mild numbness in the area and no investigations were performed.