Williams-Beuren syndrome: the prenatal phenotype

Using prenatal BACs-on-Beads technology, the first prenatal case of Williams-Beuren syndrome (WBS) was diagnosed. In light of this result, an ultrasound scan confirmed the presence of well-characterized features of WBS. This case report emphasizes the fact that new genomic technologies will generate prenatal information and provide helpful additional information.

At 25 weeks of gestation, a 22-year-old woman was referred for intrauterine growth retardation (IUGR) and nasal bone hypoplasia. The couple was not consanguineous. The woman had already given birth to a healthy boy 4 years previously and after 36 weeks of gestation. The first-trimester scan was normal, with nuchal translucency of 0.8 mm and a crown-rump length of 54.0 mm.

First-trimester integrated risk screening yielded a value of 1 in 10,000. The routine second-trimester scan found IUGR below the fifth percentile, an interhemispheric cyst, and nasal bone hypoplasia. After genetic counseling, the patients provided their informed consent for amniocentesis. In our center, all fetuses with ultrasound findings undergo prenatal BACs-on-Beads (PerkinElmer Corp, Courtaboeuf, France) screening (in parallel with conventional cytogenetic analysis) for the 9 most common microdeletion syndromes and the 3 viable aneuploidies.

Using this technique, Williams-Beuren syndrome (WBS) was diagnosed, with deletion of all bacterial artificial chromosomes (BACs) spanning the region ( Figure , A ). The abnormality was confirmed by fluorescence in situ hybridization (FISH) on metaphases with a specific probe for the elastin gene. The karyotype was therefore 46,XX.ishdel(7)(q11.23)(ELN-) ( Figure , B). After genetic counseling, the parents’ karyotypes were found to be normal.