The piebald trait is characterized by patches of skin and hair that do not show pigmentation. The hypopigmented patches of skin and hair lack melanocytes, the cells that produce the pigment melanin. The human piebald trait is a rare autosomal dominant disorder. Affected individuals generally show a white forelock, absence of pigmentation of the medial portion of the forehead, eyebrows, chin, ventral chest, abdomen, and extremities. Most patients harbor heterozygous mutations in the KIT gene. The piebald trait is also a feature of another congenital disorder, Waardenburg syndrome, which results from mutations in one of the genes EDNRB, EDN3, PAX3, SOX10, or MITF. Waardenburg syndrome patients present with other clinical features such as heterochromia iridis, sensorineural deafness, widened bridge of the nose, limb abnormalities, and enteric aganglionosis. The spontaneous mouse mutant dominant white (W) carries a mutation in the kit gene and is a model for human piebaldism.