Williams-Beuren syndrome (WBS) is a contiguous gene syndrome that occurs mainly sporadically, with an estimated frequency of 1:13,700 to 1:25,000 [Grimm and Wesselhoeft, 1980; Martin et al., 1984; Udwin, 1990]. The cases of monozygotic twins concordant for WBS and dizygotic twins discordant for the syndrome have been reported. In addition, a few familial cases have been described since 1993. The clinical diagnosis has been supported by molecular genetic findings in only two patients, however. We herein report on two families in which the WBS was inherited in girls from their mothers. All four patients showed the typical hemizygous deletion at 7q11.23 [46,XX, ish,del(7)(q11.23q11.23) (ELN/LIMK1/D7S-613x1, D7S486/D7S522x2)], but the clinical picture was strikingly variable within and between families.
