Williams syndrome (Monarch Disease Ontology identifier MONDO_0008678) is a rare genetic multisystemic neurodevelopmental disorder characterized by a distinct facial appearance, cardiac anomalies (most frequently supravalvular aortic stenosis), cognitive and developmental abnormalities, and connective tissue abnormalities (such as joint laxity). Also known as: Fanconi Schlesinger syndrome, Williams-Beuren syndrome, Williams-Beuren syndrome (WBS), deletion 7q11.23, monosomy 7q11.23.