Williams syndrome (WS) is characterized by cardiovascular disease (elastin arteriopathy, peripheral pulmonary stenosis, supravalvular aortic stenosis, hypertension), distinctive facies, connective tissue abnormalities, intellectual disability (usually mild), a specific cognitive profile, unique personality characteristics, growth abnormalities, and endocrine abnormalities (hypercalcemia, hypercalciuria, hypothyroidism, and early puberty). Feeding difficulties often lead to failure to thrive in infancy. Hypotonia and hyperextensible joints can result in delayed attainment of motor milestones.
Clinical diagnostic criteria are available for Williams syndrome; however, the mainstay for diagnosis is detection of the contiguous gene deletion of the Williams-Beuren syndrome critical region (WBSCR) that encompasses the elastin gene, ELN. Over 99% of individuals with the clinical diagnosis of WS have this contiguous gene deletion, which can be detected using fluorescent in situ hybridization (FISH) or targeted mutation analysis.
Williams syndrome is transmitted in an autosomal dominant manner. Most cases are de novo occurrences, but occasionally, parent-to-child transmission is observed. Prenatal testing is clinically available, but is rarely used because most cases occur in a single family member only and no prenatal indicators exist for low-risk pregnancies.