Mutations in Fibrillin 1 (FBN1) are associated with Marfan syndrome and in some instances with the MASS phenotype (myopia, mitral valve prolapse, borderline non-progressive aortic root dilatation, skeletal features, and striae).
A third family cosegregates mild mitral valve prolapse syndrome with a mutation in FBN1 that can be functionally distinguished from those associated with the classic MFS phenotype.
FBN1 variants are responsible for the related connective tissue disorders, grouped under the generic term of type-1 fibrillinopathies, which include Marfan syndrome (MFS), MASS syndrome (Mitral valve prolapse, Aortic enlargement, Skin and Skeletal findings, Acromicric dysplasia, Familial ectopia lentis, Geleophysic dysplasia 2, Stiff skin syndrome, and dominant Weill-Marchesani syndrome.
FBN1 encoding fibrillin-1 is a responsible gene for Marfan syndrome type 1 (MIM #154700), characterized by increased height and long limbs, ectopia lentis, and cardiovascular disorders, such as mitral valve prolapse and aortic dilation and regurgitation.