Genotype and phenotype may be correlated: Prader-Willi syndrome (OMIM #176270) is a condition associated with both a well-characterized chromosomal change (deletion of paternal copies the imprinted SNRPN gene and other genes in the 15q11-q13 chromosomal region) and a particular topography of severe self-injurious behavior (skin-picking). Here, SNRPN is linked to Prader-Willi syndrome.