Sam's changing face
Sam is a 46-year-old man who presents with an area of slowly progressive whitening of the skin on his face over the past eight years.
Each week, How to Treat publishes a clinical picture quiz.
The quiz has no CPD points attached, it's just for fun.
Take the quiz below, see how you fare against your peers and share your results via social media:
Professor Sinclair is professor of dermatology at the University of Melbourne, director of dermatology at the Epworth Hospital and director of Sinclair Dermatology in East Melbourne and Pascoe Vale, Victoria.