FBN1 and mitral valve disorder: Mutations in the fibrillin-1 gene (FBN1; MIM 134797) are responsible for disorders of the connective tissue, grouped under the generic term of type-1 fibrillinopathies which include Marfan syndrome (MFS/MIM 154700), MASS syndrome [Mitral valve prolapse, Aortic enlargement, Skin and Skeletal findings (MIM 604308)], familial ectopia lentis (MIM 129600), geleophysic dysplasia 2 (MIM 614185), stiff skin syndrome (MIM 184900), acromicric dysplasia (MIM 102370) and dominant Weill-Marchesani syndrome 2 (MIM 608328) [4–8].