Piebaldism is an autosomal dominant genetic disorder of pigmentation 
characterized by congenital patches of white skin and hair that lack 
melanocytes. Piebaldism results from mutations of the KIT proto-oncogene, which 
encodes the cell-surface receptor transmembrane tyrosine kinase for an embryonic 
growth factor, Steel factor. Several pathologic mutations of the KIT gene have 
now been identified in different patients with piebaldism. Correlation of these 
mutations with the associated piebald phenotypes has led to the recognition of a 
hierarchy of three classes of mutations that result in a graded series of 
piebald phenotypes, and to improved understanding of the mechanisms that 
underlie dominant genetic disorders.