A 14-year-old boy presents for evaluation of loss of pigment in the hair and the adjacent neck skin, present since shortly after birth. His history includes tuberous sclerosis. On examination, you note a complete loss of pigment in the posterior scalp on the patient’s left side, along with total loss of color in the skin on the adjacent part of the neck. Additional inspection reveals dart-shaped hypopigmented macules on the patient’s trunk, fleshy 1- to 3-mm papules clustered about the midface, and periungual fibromatous papules around several toenails.