Williams-Beuren syndrome (WBS [MIM 194050]) is a developmental disorder with multisystemic manifestations and a prevalence of ∼1/10,000 newborns, caused by a segmental aneusomy of 1.55–1.83 Mb at chromosomal band 7q11.23, which includes ELN (coding for elastin [MIM 130160]) and 25–27 additional genes [1], [2]. The gene discussed is ELN; the disease is Williams syndrome.