WILLIAMS-BEUREN SYNDROME IN MONOZYGOTIC TWINS WITH VARIABLE EXPRESSION

Five sets of monozygotic (MZ) twins with Williams-Beuren syndrome (WBS ) have been reported so far. We report on an additional pair, of mz tw ins concordant for WBS but variable expression for the syndrome. Altho ugh both faces look different monozygosity of the twins was proven by DNA fingerprint analysis, HLA, and blood group pattern. Both girls had the typical facial appearance with strabismus. Both had developmental delay, mild supravalvular aortic stenosis (SVAS), hypoplasia of both pulmonary arteries and multiple peripheral pulmonary stenoses, and ing uinal hernia. Unilateral renal agenesis was seen in one of the twins. In addition the pedigree pointed to a second disorder with probably au tosomal dominant inheritance. Both twins had a cleft palate, but their father had cleft lip and the grandfather as well as the greatgrandfat her had cleft lip/palate. Findings of linkage analysis in pedigrees wi th nonsyndromic oral facial cleft were taken to suggest that a major l ocus for nonsyndromal oral facial cleft is located on the distal porti on of chromosome 6. Linkage studies could serve as a starting point to examine a locus associated with WBS. Our observation and reports on t he literature support the hypothesis that WBS is a genetic disorder. ( C) 1993 Wiley-Liss, Inc.