Review Question - QID 108529

A 32-year-old African-American female comes to clinic complaining of a six-month history of skin changes in her hands. She reports that her skin has been becoming lighter around her nails, and she has had no associated itching, rashes, pain, or any other symptoms. On exam, the patient has scattered depigmented macules and patches in an acral distribution, as shown in Figure A. Wood's lamp exam confirms depigmentation in these patches. There are no other lesions on skin exam. Sensation is within normal limits and symmetric in bilateral upper extremities. Which of the following is the most likely mechanism of her disease?