Derm Dx: 'Dirty' skin that cannot be washed

A 50-year-old black male complains of brown spots on his back. He is unsure how long they have been there. The patient’s wife has tried washing them off with soap and water, but they cannot be removed. His past medical history is significant for type 2 diabetes, obesity and hypertension.

A complete physical exam is significant for brown black macules ...