DNA tells the body how to grow and function. Williams-Beuren syndrome (WS) and Supravalvular Aortic Stenosis (SVAS) are rare diseases caused by changes in a part of a person s DNA. Symptoms of both conditions include vascular problems including narrow blood vessels and supravalvular aortic stenosis (SVAS) or supravalvular pulmonary stenosis. Individuals with WS may also have developmental challenges and personality differences. Researchers at the NIH want to find out why only some people with WS and SVAS have severe symptoms. They want to collect samples and data to see what DNA or environmental changes affect the severity of the disease.