1st April 2022

A patient presents with a history of a circular, itchy lesion on her arm

A patient presents with a history of a circular, itchy lesion on her arm, which she has noticed getting worse over the past 4 weeks. You suspect a diagnosis of discoid eczema, and she confirms that she did have an insect bite in the same area before the lesion appeared. On examination, you also notice a yellow crust on the lesion. What is the most appropriate next step in the investigation? 

Select the SINGLE most appropriate investigation from the list below. Select ONE option only.