The investigators' goal is to identify the mutation in the gene that is responsible for the development of segmental dysplastic nevi. To identify the gene the investigators may use a candidate gene approach (i.e. sequence specific genes that are thought to be involved: NRAS, BRAF, etc) or a genome-wide approach trying to implicate regions in the genome (Loss-of-heterozygosity or copy number changes on comparative genomic hybridization).