Williams-Beuren Syndrome: Experience of 43 Patients and a Report of an Atypical Case from a Tertiary Care Center in India.

Williams-Beuren syndrome (WBS) or Williams syndrome (OMIM 194050) is a multisystem disorder manifested by neurodevelopmental delay and is caused by a hemizygous deletion of ∼ 1.5-1.8 Mb in the 7q11.23 region. Clinical features include cardiovascular anomalies (mainly supravalvular aortic stenosis), peripheral pulmonary stenosis, distinctive facies, intellectual disability (usually mild), unique personality characteristics, and growth and endocrine abnormalities. Clinical diagnostic criteria are available for WBS; however, the mainstay of diagnosis is the detection of the contiguous gene deletion. Although FISH remains the most widely used laboratory test, the diagnosis can also be established by means of qPCR, MLPA, microsatellite marker analysis, and chromosomal microarray (CMA). We evaluated the utility of MLPA to detect deletion/duplication in the 7q11.23 region in 43 patients suspected to have WBS using MLPA kits for microdeletion syndromes. A hemizygous deletion in the 7q11.23 region was found in 41 (95.3%) patients using MLPA. One patient had an atypical deletion detected by CMA. During the initial period of this study, the results of 12 patients tested by MLPA were also confirmed by FISH. Compared to FISH and CMA, MLPA is a cheaper, high-throughput, less labor-intensive and less time-consuming technique for the diagnosis of WBS. Although CMA is expensive and labor-intensive, its effectiveness is demonstrated to detect an atypical deletion and to delineate the breakpoints.