Clinical AdvisorDerm Dx: Black Discoloration of the Hands

A 75-year-old man visited the dermatology clinic with concerns about multiple actinic keratoses and a black discoloration on his right hand and fingers. It is noteworthy that over the past 12 to 14 years, during his retirement, the patient has experienced black discoloration on his right hand after peeling apples for pies multiple times each year. This discoloration occurs on the hand that holds his carbon knife and stainless steel peeler and typically disappears within a few days. Upon examination, the right palm exhibited black macular discoloration along the skin lines, particularly prominent on the palmar aspect of the fingers. The patient’s hands also displayed dryness and roughness upon palpation. Can you identify the diagnosis?