FBN1 and Williams syndrome: Mutations in the FBN1 gene, which encodes fibrillin-1, are associated with MFS, isolated autosomal dominant ectopia lentis 1, mitral valve-aorta-skeleton-skin (MASS) syndrome [9], Weill–Marchesani syndrome (WMS) [10], stiff skin syndrome [11], acromicric and geleophysic dysplasias [12] and Marfanoid-progeroid-lipodystrophy syndrome [13].