Williams-Beuren syndrome (WBS) is characterized by a combination of cardiovascular malformations, particularly supravalvular aortic stenosis (SVAS) and/or (peripheral) pulmonary stenosis, mild developmental delay, and distinctive external and behavioral features. Renal artery stenosis with development of arterial hypertension can also occur. Based on the external features (soft tissue fullness in the area of the upper eyelids, medially thinner eyebrows, blue iris with star-shaped pattern, full lips, especially lower lip, micrognathia, hoarse voice, small teeth standing on a gap), an early visual diagnosis may be possible. In infancy and toddlerhood, failure to thrive and digestive disorders are often found. Hernias and joint hyperextensibility are an indication of connective tissue weakness. Transient hypercalcemia is present in over 50%. WBS patients show special abilities and behaviors despite their developmental delay. As toddlers they are rather shy but later they become very sociable, eloquent and musically gifted. They mainly have difficulties in the area of visual motor coordination, e.g. in the recognition of patterns. The cause of WBS is a 1.5 to 1.8 Mb microdeletion in the long arm of chromosome 7 (7q11.23). There are 28 genes located in this region. Haploinsufficiency of the elastin gene is responsible for cardiovascular symptoms such as SVAS. Loss of LIMK1, CLIP2, GTF2IRD1 and GTF2I genes are reported to cause the characteristic external and cognitive features. In most cases, the microdeletion occurs sporadically. However, there are occasional parent-child transmissions that follow an autosomal dominant inheritance pattern. The frequency is reported to be 1:7,500 to 1:20,000.
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