Derm Dx: Black discoloration of the hands

A 75-year-old man presented to the dermatology clinic for treatment of multiple actinic keratoses and evaluation of a black discoloration of his right hand and fingers.

For the past 12 to 14 years, since retiring, the patient had peeled apples for pies several times each year. While doing so, he would develop black discoloration on his right hand, in which ...