Clinical history:

This is a seventy seven year old man who has been complaining of a persistent of erythematous plaque on his right anterior shin for more than fifteen years. He has enjoyed good past health and he is not concerned about the rash except that it is a bit unsightly. The rash is not painful or itchy. It has been there for many years with gradual increase in size. On examination, there were similar rashes found on the back and buttock. He occasionally found the rash less sensitive to change of temperature and sharp points. He was a farmer in a village of Guangdong before he came to Hong Kong forty years ago.