Francis, a 51-year-old laboratory technician of Asian descent, presents initially with a one-month history of scaly, itchy rash on his right palm. He is unable to identify any triggers. There is no known past history of any skin conditions, and family history is unremarkable. He works in a laboratory handling chemicals and washes his hands frequently throughout the day with soap and water. There are no pets in his household, and he has had no recent exposure to new soaps, moisturisers, detergents or washing liquids.

Francis is otherwise well, takes no regular medications, has no known allergies, does not smoke and drinks alcohol very occasionally. He lives with his wife and two daughters.

On examination, there is a 2cm diameter scaly erythematous plaque over the thenar eminence of his right hand (pictured). The rest of his physical examination is unremarkable.